#1
If possible, what are the notes you can leave out to make these chords only 4 notes? I was thinking the maj9#11 could just be R-7-9-#11 (skipping the 3 and 5) and the maj13#11 could be R-7-#11-13 (skipping 3, 5 and 9) but I don't know for sure and can't find a formula anywhere. Please provide an explanation if you know. Thanks.
Earth without ART, is just Eh...
#2
Contrary to popular belief you can leave the third out of certain chords. But in those i would include them in, whats wrong with 5 voices?
#3
Typically, a jazz player would opt to drop the root and fifth. The fifth won't do much except make the #11 sound grimy, and the root can be handled by the bassist. The result would be 3-7-#11-13 and 3-7-9-#11. One of the first things a jazz guitarist comes to grips with is that 3 and 7 are critical, 5 tends to be unnecessary (unless it's altered), and you have to be willing to drop the root for the sake of playability. Have fun with those chords--the #11 is where it's at.
#4
The 3rd note gives gender to a chord, i.e major or minor so that has to stay. The only note that is less significant is the 5th note, as long as it is not unaltered (ex. b5, #5)it can be removed.

Bottom line you won't have a maj9#11 chord if there isn't a 3rd,9th and #11 (obviously).
The root is not the most important note since the root is usually covered by a a bassist.
Major9#11: 3-7-9-#11.
Major13#11: 3-7-#11-13

The notes that give the chord it's name takes priority.
That's it.
#6
The 3 and 7 of any chord I've heard called guide tones, most jazz guitar players I know will start to form their chord with those two notes and add extensions on after. In this case, the maj9#11 chord I would do 3 7 9 #11 (which ends up being two major seconds stacked if you invert them) and the maj13#11 chord I would do 3 7 #11 13 (which inverted ends up being a stack of fifths).

An easy tip about the guide tones, in a maj7 chord the 3 and 7 are a major fifth apart (same in a min7 chord), and in a dominant chord they are a tritone apart.
#7
Quote by major_shiznick
Typically, a jazz player would opt to drop the root and fifth. The fifth won't do much except make the #11 sound grimy, and the root can be handled by the bassist. The result would be 3-7-#11-13 and 3-7-9-#11. One of the first things a jazz guitarist comes to grips with is that 3 and 7 are critical, 5 tends to be unnecessary (unless it's altered), and you have to be willing to drop the root for the sake of playability. Have fun with those chords--the #11 is where it's at.
This. In fact sometimes you can drop more notes as long as they are covered somewhere else. For example, if there is a piano already playing a pretty full chord, you may want to limit yourself to a few color tones in order to avoid making it sound too busy/muddy.

But, for reference, I'll just write out a (rough) list of what to throw out first (even though most of it has already been said):

1) 5
2) 1
3) Any other more clashy and/or less important notes (for example, the 11 in a maj13 chord) or notes that are covered by other instruments
4) 3
5) And finally, any extra non-color tones (e.g. in a 13#11, the b7 and #11 are the main color tones)

Now this is a very rough list (not to be followed exactly), but it gives you an idea of what you can get rid of.
Only play what you hear. If you don’t hear anything, don’t play anything.
-Chick Corea
#8
Quote by food1010
This. In fact sometimes you can drop more notes as long as they are covered somewhere else. For example, if there is a piano already playing a pretty full chord, you may want to limit yourself to a few color tones in order to avoid making it sound too busy/muddy.

But, for reference, I'll just write out a (rough) list of what to throw out first (even though most of it has already been said):

1) 5
2) 1
3) Any other more clashy and/or less important notes (for example, the 11 in a maj13 chord) or notes that are covered by other instruments
4) 3
5) And finally, any extra non-color tones (e.g. in a 13#11, the b7 and #11 are the main color tones)

Now this is a very rough list (not to be followed exactly), but it gives you an idea of what you can get rid of.
My vote goes here.
Oh yeah.

Quote by hildesaw
A minor is the saddest of all keys.

EDIT: D minor is the saddest of all keys.