I know that in dominant 7th chords the 5th is sometimes omitted but what about if you replace the 5th with a major 6th. Does that make it another chord or is it still a dominant 7 chord? Are there any other options for what chord it could possibly be?
4 Answers
A 13th chord consists of the notes {1, 3, 5, b7, 9, 11, 13}, which is the entire scale in 3rds (mixolydian if you start on 1, Ionian if you start on 5). We typically do not play all the notes and a common voicing for the 13th chord is {1, 3, b7, 13}. The 13th is the octave of the 6th so I'd say this is a 13th chord. You would want to look at all other ordering of these notes to see if it is another chord. There are multiple chords with identical notes, for example C6 = {C, E, G, A} and A-7 = {A, C, E, G}. In this case I don't see anything obvious that would make this sound like another chord.
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Saying that 11 is a part of 13 chord is misleading. At best you can say that 11 is a part of chord-scale. Jun 15, 2021 at 13:37
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@user1079505 - 11 is theoretically part of a 13 chord - the idea is use 1,3,5,7,9,11,13, which is great in theory, rubbish in practice!– TimJun 15, 2021 at 13:38
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@Tim what kind of theory are you referring to? Can you point to a reputable source saying that? Jun 15, 2021 at 14:29
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@user1079505 - not checked it out, but thought that any over 7 needed the other numbers as well - in theory. Homework time..!– TimJun 15, 2021 at 14:42
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It is a basic definition 13th is 1, 3, 5, b7, 9, 11, 13. And one does sometimes use the 11th. It depends on context– user50691Jun 15, 2021 at 15:25
The chord definitely still fulfills the function of a dominant, since it contains all the characteristic notes. Compare this well-known example in Chopin's first Ballade:
Whether to call this a 13th chord or not is a question of which theoretical school you adhere to. Personally I find it much easier to conceive of d + e + g# + c# as a straighforward dominant chord with a sustained appoggiatura tone.
answered Jun 15, 2021 at 14:48
So now, you have notes 1,3,6 and ♭7. root C - C E A B♭. It's commonly a way of playing what I call C13. That 6 becomes another 'stacked third' further up the pile. With chords which have a number greater than 7 appended, such as C9, C11, C13, often the 9 and/or 11 is omitted (although the 7 must be retained). The 5 is usually the first to go - particularly on guitar, as there aren't enough strings, or reachable places to play all the notes anyway.
However, you ask if it's still a dominant chord. Of course (assuming the 7 is flat). That ♭7 is what gets it called dominant - although the fact that it's built using the dominant note from the key helps.However, it won't be called 'dominant seventh'. It isn't a seventh chord any more, there's a 13 in there. So it's called dominant thirteenth.
You've still got the dominant root note, the 3rd of the chord, and the 7th (those last two forming the tritone which is the main 'engine' of a functional dom7 chord).
The 5th is a relatively inactive filler which is why, as you say, it is considered optional. A 6th will probably be heard as a 13th (octave shifts don't change the numbering). So we end up with a dominant 13th chord.
If the 6th/13th is just in the melody, we might still label the chord as 'G7'. If it's considered an integral part of the harmony we would call it 'G13'.
