Is C+7#9 the same as C7#5#9?

[JonR]

Agreed, sometimes a 7#11 chord might indicate the use of both a tritone and a 5th, and thus exhibit a lydian element.

Well, there's always a tritone between 3rd and 7th . As well as between root and #4/11. Not sure what different the presence (or not) of a 5th makes - except I think the chord sounds better with the 5th in it (below the #4/11)

However, while there is in theory a functional distinction between lydian-dominant and 'real' dominant (particularly when looking at scales), in chord voicings the differentiation is, from a functional perspective, rather marginal.

True.

Alt7 and 7#11 have different colours, no doubt, but they are very much related, since F#7Alt (using -5, -9) is an inversion of C7#11 and vice versa.

Yes, I was saying the same thing. The point is that C7#11 is a very different chord from C7alt! The "7#11" symbol is always - in my experience anyway - used to specify lydian dominant, and not a 7alt chord. The distinction is very useful.

In my opinion, both chord types can be used both in a dominant and / or tritone-substitution function, that is: C7Alt and C7#11 as a dominant chord to F, and F#7Alt and F#7#11 as a tritone substitution to C7.

They can be, yes, but it's quite rare to see a 7#11 used as a V. Much more common to see it as a bII (highlighting the tritone sub relationship with V7alt), or as a bVII. (When I first encountered the concept of 7#11 chords - alongside the issue of avoid notes - I saw them as potential V chords. But then I never - or hardly ever - saw them used as V chords in practice.)
IOW - as with all music theory - this is not about rules that have to be followed, but common practices. No one is saying you can't use 7#11s as V7s. It's just that, as a rule, it tends not to be done,.
Why that might be is an interesting question, but a different issue.

In this context, one needs to be mindful that any of the above chords contains 2 tritones (C F#, Bb E), and while only the C F# relationship is supported by maj3s, even the E Bb tritone can be used as a switchpoint into multiple directions (e.g., C7Alt can be understood as Bb(7 omitted) b5#5 9#9, with targets towards Eb or A). There is simply too much dynamic in these chords to make precise rules as to what to use how.

There's certainly a lot of potential flexibility, yes. But mainly that's between various types of alterations to V7s: altered scale, HW dim or wholetone. Lydian dominant is not a common alternative (on a V).

The voice-leading, of course, is what it all comes down to. There's chromaticism and half-step voice-leading involved in all the choices, and identifying a particular chord (and its roman numeral) might just come down to what bass note we use. That's the only essential difference between C7#11 and F#7alt, after all. Both lead (conventionally) to Bm or B, in the same way. C7#11 just gives us a half-step bass move.
The mix of chord tones and chromatics we choose, to enhance the cadence, is what gives rise to the chord identity, rather than vice versa. And the fewer notes in the chord, the more options for other scale notes and therefore chord/scale choices.

I come from the piano, and looking at C7#11- Fmaj, this simple passage works fine for me:

Less so for me, but only because of the b9 (or rather augmented double octave, as notated!) between the Gb in the bass and the G above.

[eh6794]

I dont know if this has been answered, but the "+" sign as very specific in what tone gets altered. Thats an augmented sign, so no, both chords are not the same.

[henryrobinett]

Huh?

[henryrobinett]

So Augmented 5th and #5 are not the same?

[mr. beaumont]

Good lord, the advice dispenced gere sometimes...

[eh6794]

They are the same. I read a post that said it should be read as an altered chord. An altered chord could mean flat or sharp. The C+7#9 is a sharp 5th, not a flat 5.

[eh6794]

Ohhhhjjhjjhhhh shhhttttttttt. I noticed the #5 in the second chord. Brain fart. Sorry, go back to what everyone was doing

[mr. beaumont]

Its cool. I typed "gere." Ive needed several saissons to keep up with this blackhawks game...

[henryrobinett]

Lol! It's all good.

[AlsoRan]

Ohhhhjjhjjhhhh shhhttttttttt. I noticed the #5 in the second chord. Brain fart. Sorry, go back to what everyone was doing

Thanks for putting yourself out there to help. Nobody is perfect, right?

[eh6794]

Right!

[Vladan]

Its cool. I typed "gere." Ive needed several saissons to keep up with this blackhawks game...

G is augmented version of H, anyway.

[Space Pickle]

Blackhawks are toast booyeah

[fumblefingers]

Agreed, sometimes a 7#11 chord might indicate the use of both a tritone and a 5th, and thus exhibit a lydian element.

However, while there is in theory a functional distinction between lydian-dominant and 'real' dominant (particularly when looking at scales), in chord voicings the differentiation is, from a functional perspective, rather marginal. Alt7 and 7#11 have different colours, no doubt, but they are very much related, since F#7Alt (using -5, -9) is an inversion of C7#11 and vice versa.

In my opinion, both chord types can be used both in a dominant and / or tritone-substitution function, that is: C7Alt and C7#11 as a dominant chord to F, and F#7Alt and F#7#11 as a tritone substitution to C7. The use of both the -5 and the 5 in C7#11 creates an interesting tension, and it all depends on the voicings how to resolve those.

In this context, one needs to be mindful that any of the above chords contains 2 tritones (C F#, Bb E), and while only the C F# relationship is supported by maj3s, even the E Bb tritone can be used as a switchpoint into multiple directions (e.g., C7Alt can be understood as Bb(7 omitted) b5#5 9#9, with targets towards Eb or A). There is simply too much dynamic in these chords to make precise rules as to what to use how.

I come from the piano, and looking at C7#11- Fmaj, this simple passage works fine for me:

do you view the 9#11 chord as a dominant IV chord in melodic minor?

[JonR]

do you view the 9#11 chord as a dominant IV chord in melodic minor?

IV chords are "subdominant", by definition .

Technically you're quite right that 9#11 is diatonic to melodic minor as a IV. I've personally never seen one used in that way. (That's mainly because minor key chords are not generally harmonised from melodic minor, other than the tonic.)

However, 7#11s can occur as IV chords in major keys. They make a bluesy alternative to the usual maj7#11. I personally like to use one on the IV in Moon River.

Phil in London is also quite right that in theory a 7#11 chord could be used as a V chord (dominant function). I can see no reason why not, and plenty of reason why it ought to work. The question, perhaps, is it ever done in practice? And if so, in what contexts?
I'm pretty sure I have seen lyd dom chords used as V7s; but quite rarely. The question then is: why so rarely (if theory suggests it's OK)?

So it becomes an issue of how seriously one takes "common practice". Do we want to be bound by common practice (in order to sound conventionally "correct", follow the accepted traditions of the masters, recognisable "jazz" idioms), or do we want to experiment? Move beyond?

As a choice, that might seem like a no-brainer, but it's a useful perspective, IMO.