Quick question about 13th chords; is it a Major7 or Dom7?

[popcornn]

Hi,
If for example on the tonic of C I have a 13th Chord, is the 7th B or Bflat (Major or Dom7th?)

So a 13 Chord on C would be:

C, E, G, B, D, F, A
or
C, E, G, Bflat, D, F, A
How would the symbol for these be witten, C -7 13? (for a dom 7th 13th) I'm confused.
Thanks everone.
p.s. If you can, what would Am13th Chord be?

A,C,E,G,B,D ?

Thanks again.

[ajspiano]

its a flat.

Typically when its a 13th chord its dominant, so in C the 7th is Bb. If it were a Major 7th tonality it would be expressed as a 6. Notice the 6th and 13th are the same note?

[Bob]

They just write C7 for a dominant seventh.  C -7 looks like C-7, c minor seven.  

Just think of it all on a major scale, esp for the extended part of the chord.  It's really just a major 3rd, unless it's marked minor.  Dominant, unless marked major or minor.  Fifth is the same, a fifth, unless it's altered.  And the 9th, 11th, 13th are from the major scale until they're altered.

a c e g  b d f#    
I'm not an expert on extended chords, but I did read that you're supposed to avoid minor ninths because of the clash.  So between the fifth and thirteenth, you end up with a M9 too instead of a m9 (clash).  [And if you go up to 15th chords (which I haven't really heard of but they fit the hand well) you end up with a clash either way on some of the chords.]

I know how to create them, extended chords.  What I'm less familiar with is which ones are more common and the voicings for them.  And if the extended notes -- 9, 11, 13 -- really have to be at the 9th, 11th, and 13th or whether it's still a 13th if you make a M6 chord.  And if you have to have all the 'filler' notes if it's an extended chord or not, like a 13th spelled C E G Bb A vs. C E G Bb D F A.

I've got a few threads on this if you want to search for them.  Probably on the student board or theory board.

[nystul]

It seems that the convention is to call the note 13 on dominant chords and 6 on major or minor chords.  So you probably won't see a "minor 13th" chord.  One option maybe for C13 would be to stack fourths around middle C like Bb-E-A (or with both hands, Bb-E-A-D-G-C).  That's a very cheap trick jazzy sound that I like quite a bit.