I do actually think that a G7#11 (no 5) is a better notation for the improviser than G7b5, because with the first option the improviser will immediatly know that the 4th mode of the melodic minor , with an ommited natural 5th, will be "right".
{But see, this is the problem--who says that mode is "right"? Why shouldn't I see a G7b5 and play a whole tone scale or an altered scale, either of which will include G B/Cb F A? You're assuming that when somebody writes G7b5 in a major key, you're "supposed to" play lydian dominant, because they really meant G7#11 no 5. What basis is there for assuming that?}
If the same person sees G7b5, I think he's likely to be confused about what alterations are implied inside that harmony.
{There isn't one set of alterations that are implied by that chord, or ANY 7th chord for that matter. That's one reason people often just write 7 on charts--they leave it up to the player to figure out what alterations to play. That's not confusion, that's being open-ended and trusting the player.}
Since G7b5 (as far as I know) can't be derived from a particular scale
{How about the whole tone scale? And who says a chord has to be derived from any scale? But in any case, a lot of jazz works not by technical correctness but through enharmonic equivalence. You mentioned the 7th mode of the mm. Technically, there is no natural 3 in that mode. If you take that mode from G to G, it goes G Ab Bb Cb Db Eb F G. But that doesn't stop us from making that Cb function like a B over a G dominant chord.}
and is not really a common chord in jazz,
{Not true in my experience. As Phil pointed out, the Sher Real Books--which IMO are vastly better edited than the Real Book and any other fake books I know of--are full of thing. Consider also that many, if not most, of the Sher charts were reviewed if possible with the composers and thus are more likely (albeit not certain) to reflect the composers' intentions and practice than the average fake book would be.}
there is really no practical way to know which scale corresponds with that chords, imo.
{Sure there is. First, there can be more than one scale, depending on what you're trying to do. IMHO it's not always so much about finding the one scale that works as it is about knowing what the possibilities are and how they would sound. Second, just listen to the rest of the piece! A chord doesn't exist in a vacuum, it's coming from somewhere and going somewhere. }
/lovebown
