Wednesday, November 4, 2009

Collecting Royalties as a Composer

Q: Hi Chris!
I took your music business class at the Los Angeles Music Academy last year. I need some help with a situation that has come up with my career. I am currently in Phoenix recording my first record. One of the songs I wrote, another band really liked and wants to record. I'm totally happy about that and want to let them do it. I also want to make money for letting them use it. I'm not really sure what the rules are here and I don't want to get screwed. If you could give me any advice I would really appreciate it.

A: Hey that's great! I would suggest that you should make a publishing company as a DBA. register with BMI as a publisher and writer. This will make sure that you collect performance royalties when the song gets played on the radio, in film or TV. As you'll recall from the class, as a composer you are entitled to points when a CD gets sold. You can get paid directly for mechanicals from the record company or sign with harry fox to administer and collect (maybe this is better as you don't have much experience).

A DBA stands for "do business as." More about that here:


Sunday, September 27, 2009

Blues Power

Q: I was reading your blues lesson on your site and am wondering: what do you think makes the Blues greats, great? I mean, what do they have that all the others don't?

A: Man, what a question! It is really hard to talk about Blues from a theoretic point of view but I'll give it a shot. First let's just talk about the few things you have to have:

1. A complete understanding of the chord changes when you solo - This means you really have to be able to hit the right chord tones as the chords come by, to the level that you can stop thinking about it and your fingers know the way. That is why simply playing the minor and/or major pentatonic scale over the progression doesn't guarantee you anything but a very mediocre solo although it is a start.

2. Knowledge of at least some of the traditional licks - You see, even playing the right scales and chord tones doesn't guarantee you a great solo either. There is a definite vocabulary and the only real way to be able play an effective solo is to learn the vocabulary from the best. You have to know where the licks work too: the I, IV, V and turnaround licks for example. If you copy from a wide variety of players, you'll be sure to not sound like any one player and eventually a little time with them under your fingers will lead to a natural evolution of the phrases and your own personality will start to emerge.

3. Good Blues Tone - I'm not saying your tone has to be just like everyone else's but there is a generally excepted tone that involves a certain amount of warmth and/or twang. Of course there is a wide variety of this tone, from Strats and Teles to Les Pauls, but you know it when you hear that Blues tone. You certainly are going to have a rough time milking it from a Roland Jazz Chorus amp.

4. Power - I'm not sure how to describe this, but let's just say the greats all have this power that just knocks you out. It isn't really a technical thing but just this overwhelming sense of strength. Take a look at the great Freddie King and see if you don't feel it:

Saturday, September 26, 2009

Guitar Tools pt.2

My second installment of the column I write for This one is dedicated to treble boosters and especially the most famous one, the Rangemaster.

Treble Boosters
– As we learned in part 1 of this column, guitarists in their quest for rock and roll tone often turned to fuzzes to push their amps to the breaking point, but another group of guitarists used a different device. To add some sparkle to the dark British amps in the sixties, many guitar players turned to treble boosters. In addition to adding more high frequencies, they also helped drive their amps with a dbl boost and some added distortion. Although a very 60s sound, the treble booster sounds completely different than the fuzz but if you want and need a varied classic type sound, having one of these in your bag is a must. More >>>

Thursday, September 17, 2009

Recording Advice

Q: My band is recording our first EP in a couple of weeks. Could you please share any insight on how you prepare to perform your guitar parts in the high pressure, clock ticking environment of the recording studio? I don't mean engineering advice, but performance/guitarist tips or even mentality. So far I've been woodshedding the most difficult guitar parts I have to pull off (two shred solos) at home. I record myself, listen back and work specifically on the parts that get sloppy. I play them out of time, then with a slow metronome speed, and then finally up to speed with my goal being to eliminate unwanted noises and to play each note clearly in tune and in time.

A: If this is your first time in the studio, it will be an eye opener. Since the session is your own, there are different thing to consider as opposed to a session for someone else. In some ways it is a lot less pressure, because after all the time is your own and not somebody else’s. Things you might want to think about besides your guitar parts:
1. Get the endings and intros straight before hand. Rehearse your band and figure out how you want to end the songs. Live endings and recorded endings are usually different. Live endings, you bash out a chord and your drummer does a fill and you end it and he play another drum fill. In the studio, you usually don't do live endings that way. Have a listen to various studio recordings and check out how the bands end the songs. For reference, here is two versions of one of my songs, check out the endings. You’ll have to click on the titles of the songs individually but there are four live version songs of songs that appeared on my second CD, compare them and see.

Have a listen to “House on the Hill,” and “Tell me A Story” here:

and then have a listen to the studio cuts here:

You would be surprised how much time gets sucked in the studio on intros and endings so try to get it straight a head of time or you'll end up rehearsing on studio time.

2. Rehearse your band with a click track. If you guys can't play to a click, you will also suck time trying to get in sync. This goes for your guitar parts as well, practice them to a click or rhythm track, this will help you lock in when the time comes.

3. Figure out how to play without any effects on your guitar. Ambient effects definitely come after you record your part so get used to doing it that way. You can use distortion, just make sure you turn it on at the very last second because it is noisy. As it is your time, the engineer might not say anything about you bringing delay or reverb but it will ruin your sound possibly and maybe even make your part unusable if your delay rhythm is different than the song tempo. It is much better to record dry.

4. Get you headphone mix right before hand. Since you have to play dry, have the engineer send you back your guitar mix wet. I sometimes have him send it back really wet, even wetter than I would have him mix it, but this can make it very easy to record. Don’t forget, what effects he sends back to you in your headphones, doesn’t stay in the mix. If you are not sure how to describe what you want, and you are used to playing with a wet sound, just ask him to send it back with about 700 ms and two or three repeats. Maybe have him give you one channel dry guitar and one channel effects on your little groovy headphone mixer and you can mix it there yourself.

5. Try to record Drums, Bass and guitar together. You can throw away the guitar track later so it doesn’t matter if you screw up or not. Your guitar part is just to help your drummer and bassist keep track of where they are in the tune. If you are using a vocalist, it also helps to have him sing as well just to keep everybody true to the form. As I said you can scratch the tracks later and redo them. If you don’t have any booths, you can record your scratch track direct. You bass player will most likely get recorded direct anyways so you can all be in the room with the drummer this way. You can of course move your amp into a booth if there is one but as you are throwing away the track anyways, it doesn’t make much difference. When you record your guitar part (the one you are going to keep), if you have a big room, you can be in there with your amp. I tend to record this way a lot. It helps if you keep the amp far away from you because the loud amp can overwhelm your headphone mix leading a variety of problems. You should definitely practice through the amp you will be recording with because if you practice through something else, the difference in tone might be enough to throw you off.

6. As far as getting nervous, there is no real reason to. As I said, it is your project and your studio time so you shouldn’t feel pressured. The time you should feel pressured is when you are recording for a pain in the ass producer who wants the perfect guitar part done in ten minutes. But if you are having a real hard time getting it together, just simplify. It might help to prepare a simpler part ahead of time if you really need to be out quickly. If worst comes to worst, record the other parts for all the songs minus the guitar solos first, because you can always do your guitar parts after the fact without your band there to bug you. So even if you need an extra day, you can knock out your tracks in one day.

7. If it is a pre-written part, make sure you have it 120 percent down because you lose about 20 percent because of nerves.

Hope this helps,

Sunday, August 30, 2009

Dominant Pentatonic Scale

Q: I read a column about the dominant pentatonic and I'm feeling a little confused. Here's why... The dominant pentatonic comes from the Mixolydian Scale, and I know this mode and have no problems with that. Now the pentatonic takes only five notes of this scale. My problem here is what are these five notes? The Mixolydian looks like this: 1-2-3-4-5-6-b7 What should be the formula for the dominant pentatonic? Should it be this: 1-3-4-5-b7 (referenced here >>>): 

Or should be this one:
1-2-3-5-b7 (referenced here >>>):

Because in fact both use only five notes, and in both, the five notes come from the Mixolydian Scale, so which one to use? I've seen in several places the first one, and in others the second one. Thanks a lot for any info!

I can see how this might confuse you. Let me see if I can shed some light on the subject. First of all, you'll be happy to know that there is no set standard pentatonic scale called the dominant pentatonic scale, so there might be several different examples floating around out there. As you probably know the most common pentatonic scale used for dominant chords would be the minor pentatonic: 1-b3-4-5-b7.

The examples you picked up are synthetic pentatonic scales, for the lack of a better name. Now this does not mean that they are wrong or anything and are fine to use in the right circumstances. Pentatonic simply means five notes so there are plenty of combinations you could make from any 7-note scale. Now the first one you describe is a common synthetic pentatonic scale that was probably made popular by Jan Hammer (matter of fact, I have heard it referred to as the "Jan Hammer Scale" before.

Here is the trick with this scale and how you can do the trick to make different pentatonic scales. Before I do this, let's make sure you know exactly what the "standard" two western pentatonic scales are. They basically eliminate the half steps from both the major and minor scales:

Major Pentatonic: 1-2-3-5-6

Minor Pentatonic: 1-b3-4-5-b7

These "standard" pentatonic scales work well with the 7-note modal scales because the same pentatonic scales work as good replacements for most of the modal scales. In other words the major pentatonic (
1-2-3-5-6) can be found in the three major modes (ionian, lydian and mixolydian) and the minor pentatonic (1-b3-4-5-b7) can also be found in the minor family modes (aolian, dorian and phrygian):

Ionian: 1-2-3-4-5-6-7
Major Pentatonic: 1-2-3-5-6

Lydian: 1-2-3-#4-5-6-7

Major Pentatonic: 1-2-3-5-6

Mixolydian: 1-2-3-4-5-6-b7

Major Pentatonic: 1-2-3-5-6

Nothing changes here right? How about the minor modes:

Aolian: 1-2-b3-4-5-b6-b7

Minor Pentatonic: 1-b3-4-5-b7

Dorian: 1-2-b3-4-5-6-b7
Minor Pentatonic: 1-b3-4-5-b7

Phrygian: 1-b2-b3-4-5-b6-b7
Minor Pentatonic: 1-b3-4-5-b7

Now let me explain what we will call, modal pentatonic scales. Again this is my description and just like there is no standard term like "Dominant Pentatonic" there also is no standard term "modal pentatonic." But let's just use the term for the lack of a better one. What we are going to do is use the formula for the minor pentatonic (
1-3-4-5-7) and use it for the major family modes adjusting the intervals accordingly. After that, we will take the major pentatonic formula (1-2-3-5-6) and apply it to the minor modes.

First let's take the minor pentatonic (1-3-4-5-7) formula and apply it to the major family modes starting with mixolydian. We will have to lower the 7th because the mixolydian scale has a minor 7th:

Mixolydian: 1-2-3-4-5-6-b7
Mixolydian modal pentatonic: 1-3-4-5-b7 (based on the formula for the minor pentatonic scale) This is the scale that was referred to as the "dominant pentatonic scale," we made it by applying the minor formula to the mixolydian scale.

Lydian: 1-2-3-#4-5-6-7
Lydian modal pentatonic: 1-3-#4-5-7

We can take the major pentatonic formula (1-2-3-5-6) and apply it to the minor modes as well:

Dorian: 1-2-b3-4-5-6-b7
Dorian modal pentatonic: 1-2-b3-5-6

Phrygian: 1-b2-b3-4-5-b6-b7
Phrygian modal pentatonic: 1-b2-b3-5-b6

Aolian: 1-2-b3-4-5-b6-b7
Aolian modal pentatonic: 1-2-b3-5-b6

Locrian: 1-b2-b3-4-b5-b6-b7
Locrian modal pentatonic: 1-b2-b3-b5-b6

So there is how your first dominant pentatonic scale comes about.
Your next example is also just synthetic and the person who made it simply eliminated the 6th from the major pentatonic scale and replaced it with the b7th from mixolydian.

Mixolydian: 1-2-3-4-5-6-b7

major pentatonic: 1-2-3-5-6

synthetic: 1-2-3-5-b7

Another great pentatonic scale for the Blues can be made by replacing the b7 in the minor pentatonic scale with the major 6th. That scale looks like this: 1-b3-4-5-6. I love this sound and use it all the time in the Blues. The major 6th in the scale gives you a super major sound over the I chord and the same 6th in the scale becomes the major 3rd over the IV chord.

There are actually countless pentatonic scales used all over the world, for example this one used by the Japanese in Okinawa: 1-3-4-5-7

To make this even more confusing, you can also superimpose various pentatonic scales over individual chords for outstanding results. Just for example:
Lydian = minor pentatonic on the 3rd, 6th and 7th (E lydian = G#, C# and D# minor pentatonic scale).

But as far as I know, there is no one standard dominant pentatonic scale. So as far as which one to use, whichever you like is fine.


Sunday, August 9, 2009

Modes and Slash Chords

How are you? I was just going over some of your lessons online and found them very interesting. I do have a question:

I am currently using the C Mixolydian mode to jam/solo over the root of the mode (C). I am very confused on what chords to use. I saw a video of Frank Gambale explaining this but I can't understand this. He mentions to use the 4th and 5th chord of the major scale. To me, the major scale of C mixolydian is F major...correct??? do I play a B and C? If I am wrong, what am I doing wrong??? I would appreciate any help

Glad you like the lessons. You have to understand the diatonic system to use the modes properly. As you described, you always use the mode over the diatonic chord of the same name right? So C mixolydian works over a C7 chord. Here is the diatonic system for C mixolydian, the key is F major:

I - F (or Fmaj7) - Ionian
ii - Gmin (or Gmin7) - Dorian
iii - Amin (or Amin7) - Phrygian
IV - Bb (or Bbmaj7) - Lydian

V - C (or C7) - Mixolydian

vi - Dmin (or Dmin7) - Aolian

viio - Edim (or Emin7b5) - Locrian

Now probably what Frank is saying, is that the IV and V chords of this key, played over the root of the mode are good slash chords to play for a modal vamp. The IV and V chord in the key of F are Bb and C right? So play these over the C root, as in: Bb/C - C/C (C/C is really just a C triad). So this is a good progression to jam on. This will work for any of the modes:

Bb lydian for example: Bb and C over the lydian root: Bb/Bb - C/Bb (really Bb - C/Bb). This is good for Bb lydian.

D aolian: Bb/D - C/D

A phrygian: Bb/A - C/A

All these examples are simply the IV and V chord played over the modal root. Of course this is just a simple way to practice and you can simply make up progressions from the modal chord. Just don't mix up the chords too much or you will lose the modal sound. Two chords are usually best. C mixolydian: C7 - Dmin7 or C7 - Bbmaj7 for example.


Tuesday, July 21, 2009

Mixolydian vs. Lydian Dominant

Q: I have to play a solo over a C9 vamp, and I realize I have several scale choices. let me see if my theory is correct here: The mixolydian scale is totally diatonic, but the #4 in the lydian dominant scale works because the ear also accepts the blues scale (b5), right? So in a way, the lydian dominant works like a pivot between inside (diatonic mixolydian) and out (blues with b3 as well), which also lets the Dorian work sparingly too. Does that sound about right? (or am I trying to get into heaven here?)

You pretty much have it but not completely: Some people would argue that lydian dominant is actually more inside than mixolydian because the natural 4th in mixolydian would technically clash with the major 3rd in the C9 chord. There is some truth in this I think. Technically lydian dominant has no "avoid note" so to speak, the #4 being far enough away from the 3rd in the chord. Some players would tell you, me too for that matter, that mixolydian is better used for a 7sus4 chord. It is all a matter of taste I suppose. C Dorian would only work over a C9 chord because it sort of looks like a combination of the C major pentatonic and C minor pentatonic scale. But it leaves out the most important note, the major 3rd. And it seems clumsy (too big) for blues. So I think that a C dorian scale over a C dominant chord isn't really a great choice.
Also, I wouldn't put the cart before the horse, meaning that I wouldn't think that (as you said) a scale is diatonic to a chord, it is really the other way around: chords are diatonic to scales. So C9 is diatonic to both C mixolydian and C lydian dominant. But you are right to think that we like the sound of the b5 because it reminds us of the blues scale (again, a matter of opinion).

Besides the major and minor pentatonic scales, mixolydian and lydian dominant, you can also create some tension by using the half/whole diminished scale.

I've posted on dorian over a blues before. Here>> Other links:

Sunday, July 12, 2009

The Whole Tone Scale

Q: What can you tell me about the whole tone scale? I didn't find anything on your site regarding it.

A: The whole tone scale is used in very specific situations, so I didn't mention it too much in the lessons on But it is a valuable scale to know and has one very interesting application that took me about 20 years to figure out. First of all, it is a 6-note scale which is unusual in itself. It is a symmetrical scale, meaning it is based on a set of specific intervals that repeat. The half/whole diminished scale (an 8-note scale) is also a symmetrical scale based on a repeating half-step, whole-step pattern. The whole tone scale is a pattern of all whole steps. So for C: C-D-E-F#-G#-A#. If you harmonize it, you will get a C7#5 or C7b5 chord. When you add in the 9th (D, in this case) something strange happens, you get a C9 chord with a b5 or #5. How strange is that? I've actually run it to one or the other on a few charts but it is rare and sounds somewhat strange. You have to be weary of using the scale because a lot of guys will add in an altered 9th on a 7#5 chord, thinking altered rather than whole tone. I like to use it on chords that are specifically #5, like in "Stella by Starlight" when that G7#5 chord pops up. It is a real abstract sound, I've heard it described as Bambi disintegrating. I suppose the fact that all the intervals being the same distance apart give the scale a sort of nebulous vibe. You hear it sometimes in movies or TV when somebody goes into a dream or fantasy scene. Anyways, that's how I hear it.

I actually use it more in another application than the standard, over the 7#5 chord.
I like to use it a half step down on a minor chord. You have to be daring and have good improv sense to make this work because it is outside. It is a good way to play outside on minor chords and works well if you sandwich it between two inside minor scales, like dorian. It can be justified as well. Here is a B whole tone scale: B-Db-Eb-F-G-A, now let's look at the intervals comparing it to C minor: B is the major 7th (like melodic minor), Db is the b9th (as in phrygian), Eb is the minor 3rd (like all minor modes), F is the 11th (like all of the minor modes), G is the 5th (like all the minor modes except locrian) and A is the 6th (like dorian). No root!

This was a good subject so I put together a whole lesson on the subject: The Whole Tone Scale

Tuesday, July 7, 2009

Cissy Strut

Q: I had a quick go of "Cissy Strut" last night. I'm trying to figure out the progression. If you look at it in Eb you get a vi-ii-V which seems on the money. I've tried some improvising and C blues or minor pentatonic fits, as does C Dorian and C natural minor. However, I was trying to figure if you can analyze the sequence from C harmonic minor perspective, since the tonal is so clearly a centerCm key (the Eb relative major is only implied, right?) But that gives a i-VII-IV which seems screwy... any ideas?

A: I wouldn't think too much about this one. I mean if God came out of the heavens and said; "Chris Juergensen, entering heaven will depend on how you analyze 'Cissy Strut,' the famous New Orleans funk hit covered by many musicians, what are the three chords in relation to each other?" I would say; "Thanks for this chance to get into heaven God, here is my answer: The C chord is a 'I' chord, the Bb chord is a 'bVII' borrowed from C minor, and finally the F chord is a 'IV' chord." And he would most likely let me into heaven despite all the rotten things I have done to various women over the years. But if he was anything like me, and this is very unlikely, he would say; "You are thinking too much about it, just play a blues have a good time."

Thinking minor is not such a good idea with this tune. It is only minor the same way a Blues is minor, meaning the minor pentatonic scale will work, but the chord is really a C7 chord.

Strut if a fun song to play if you are adventurous, It is basically a A-A-B-B form with both the As and the Bs in C. Scofield changes the B section to the key of Ab I think. When I have my students play it in their ensemble class, I make every guitarist change the B section to something different. It makes the song fun but also makes the solo a bit more challenging.


Monday, July 6, 2009

Playing Over "Impressions"

Q: I´m playing the song IMPRESSIONS in D-7, but when I play F melodic minor it sounds good, tell me why?

Good question. I'll take you through my thinking process rather than just give you my answer: Let's see, F melodic minor: F-G-Ab-Bb-C-D-E, now let's look at the scale from D, as that is the chord you are playing it over: D-E-F-G-Ab-Bb-C. That gives us a 1-2-b3-4-b5-b6-b7. Ah, this is the locrian #2 mode from melodic minor. This is a very common scale for a min7b5 chord, much better than the locrian scale or harmonic minor that a lot of guys might use. Although, not the most common choice, it is one choice for a min7 vamp like Impressions. Other choices: D dorian, A, D and E minor pentatonic, D melodic minor and if you are really daring, Ab melodic minor. Check out this
scale/arpeggio guide and try some different things. This is a lesson dealing with locrian #2.

Friday, July 3, 2009

Modes and Chords

Is there a simple way to remember the which major scale equals what mode and the chords they work over?

A: I wish there was a quick method but I'm not sure there is one. You just have to remember the rules, which are:

Dorian = major scale down a 2nd. (Ex: C dorian = Bb major)
Phrygian = major scale down a 3rd. (Ex: C Phrygian = Ab major)
Lydian = major scale up a 5th. (Ex: C lydian = G major)
Mixolydian = major scale up a 4th. (Ex: C mixolydian = F major)
Aolian = major scale up a minor 3rd. (Ex: C aolian = Eb major)
Locrian = major scale up a minor 2nd. (Ex: C locrian = Db major)

The chart above might help put things in perspective.


Tuesday, March 3, 2009

Playing Guitar and Antarctica

Q: As my sightreading reaches more acceptable levels I look to consider comping on cruiseships in a ‘Jay Leno’ style pit band. Although it is not a first choice, it will at least be something professional top put on my CV, as well as a chance to play something beyond party tunes, and to further improve reading skills and save. How well respected are people who have done cruise gigs? Will it open any doors on my return? I’m 25 now and I feel like if I don’t do something it will be too late. I can’t think of any other options at the moment. Some wisdom from someone of your experience and calibre would be fantastic.

I'm not sure that a boat gig (as we call it in musician circles), in itself commands any real respect. What does command respect is a musician who consistently works, be it a boat gig, plus anything else for that matter. A good friend of mine just went on a boat gig, he is a year younger than you and a very fine guitarist. He asked me what I thought about the job offer on the boat. Some other musician who was there at the time gave his two cents, which I thought was a load of crap. He said that a boat gig does nothing for one's career and should be avoided. I told him this: that it doesn't matter what the gig is and a gig is a gig and should not be turned down unless you are sure that there is something better on the way and the boat gig would ruin your chances. You see, it is a privilege to get paid to play a guitar. Think about it, it is a piece of wood with some steel strings attached and when you hit them with a little piece of plastic, somebody gives you money and you can get babes too. What a concept, it seems to good to be true! Some people even give me money to show them how to pick at the strings with the plastic thing so they can get paid too. So when you start wondering if a boat gig will pay well or commands respect, the answer is that any job you can do with a guitar in hand commands respect and any amount of money is overpayment for such a fun thing. And I'll tell you when he emailed me a photo of Antarctica, i really thought so. How many people get to go to Antarctica? And how many of them get paid to go? And how many of them get paid to go to Antarctica by hitting some steel strings on a piece of wood with a plastic thing? Pretty amazing if you ask me. I suppose that there are better paying gigs but so what? Hopefully it is just one gig in a series of gigs that will stretch on and on. Plus, you never know who is on the gig. One of the guys on the gig could go on to a real big gig one day and take you with him.
If you can get yourself on a boat gig, pat yourself on the back my friend and welcome to a very exclusive club, the club of professional musicians.

Sunday, January 25, 2009

3rds and 4ths together in chords

Q: Why is it that major 3rds and 4ths in the same chord is prohibited? In your book (p.49) You say that simultaneous presence of a major 3rd and perfect 4th in the same chord is undesirable – so, why exactly? Because it’s said to be cacophonous? And that’s all? Hmm… Maybe there are some reasons which are more objective? "Cacophonous" is too subjective to my mind (especially regarding modern music)… As I understand it, any two notes a min2nd (or min 9th) apart never should present in the same chord simultaneously. But later in "The Infinite Guitar" while regarding different modes You give a lot of examples of chords with simultaneous presence of one and even two pairs of notes min 2nd (or min 9th) apart. How could You explain all this?

3rds and 4th together in the same chord is not prohibited, just not a great sound. Sometimes minor 2nds together in a chord sound better than others, like between the 7th and root in a maj7 chord or between the #11 and 5th in a maj7#11 chord. Even between the 3rd and #9 in a 7#9 chord. So why not in a sus chord? Because:
  1. It throws the nature of the chord into question. In a maj7 chord the B and C notes are important to the nature of the chord (the chord sounds crappy with the 7th as the bass note but eliminating either, would change it from what it is), same with the #11 and 5 in a maj7#11 chord. A 7#9 chord without both the major 3rd and #9th would turn the chord into something else. But the 3rd and 4th in a dominant chord are conflicting to the nature of the chord. It makes the ear wonder if something is wrong and confuses us.
  2. It isn’t necessary. The 4th is way more important in a sus chord and there are better notes to add to the chord than a 3rd.
By the way, theory is just common practices to specific genres and, although sometimes based on laws of nature, is not musical law. You can add a third and there are some interesting voicings. Like a IV–V in G (C–D). Play an open position C chord and slide it up a whole step leaving the 3rd and 1st string open. Nice sound as long as you are arpeggiating and not bashing the chord (look at the chord up on top of this post).

C-E-G-B-D-F-A (maj13 chord) = also impossible? Why? For the same reason, the 3rd and 4th can't be included together in the same chord? But is the 11th note is necessary for the 13th chord?

A: No, theoretically the only notes that must be included in a 13 chord (major or minor) is the 1-3-5-7 and 13. 9ths and 11ths are options. But the general rule is that the 11th, if you were to include it should be raised, as in C-E-G-B-D-F#-A. But once again, they are options and regardless, you couldn’t play a 7 note chord on the guitar. If you were playing with a bassist, you could technically just play the 3rd, 7th and 13th.