[hedzeppelin]

Same deal with chords. I don't usually use 11th or 13th chords. However, if I'm in a situation that calls for them, I can play a 7th chord, and it will fit.
It won't give the coloration that the 11th and 13th chords render, but the 11th and 13th chords are derivtives of the dominant 7th chord family. Bearing
in mind that chords are formulated from the major scale:

C major scale

1......2......3....4....5....6....7
C......D......E....F....G...A....B

Now, the formula for a dominant 7th chord is: 1,3,5 b7.
Therefore, the notes in the C7 chord are:C,E,G,Bb

The formula for an 11th chord is: 1,3,5,b7,9,11

Well...wait a minute...there are only 7 notes in the major scale! How do we
get "9" and "11"? Simple. "9" is actually "2" and "11" is actually "4".

1......2......3....4....5....6....7
C......D......E....F....G...A....B
........9...........11........13

So, the notes in the C11th chord are: C,E,G,Bb,D,F.
Note that the first 4 notes comprise a C7th chord.
So, if I play a C7 chord instead of a C11 chord, it will indeed fit.