I'm hoping for a vibraphone with a more defined richer timbre. The one in Plugsound Vol 1 is phenomenal.
I'm also hoping for a much more extended brass, strings and woodwinds, which is what I believe GPO Advanced will be offering. I'm thinking of the sarrusophone, serpent, opheoclide, curved trombone, mellophone, cimbasso, wagner tuba, euphonium, alto and soprano bassoons, double valve tuba, helicon, hecklephone, classic saxophones, now for strings, baroque and renaissance lutes, vintage violins, violas, cellos and doublebasses, a triplebass one-string cello (like a super-doublebass but with richer harmonics), classical guitar and some more exotic harps. Now for woodwinds, contrabass flute, sopranino clarinet, kazoo, thunder machine, piccolo reed (an exotic curved clarinet that has very warm high order harmonics) and of course, more percussion would round it off nicely.
Anything I haven't listed? Wow, I'm breaking out a sweat. There must be dozens and dozens of these rare and exotic instruments. Of course, 1000 instruments would be too many...so sticking with the ones that are known to be used more commonly (I say more commonly because some instruments were invented but were never used).
Ben, if you didn't put Contrabass Clarinet in your list, then I'd like that one too. I find its lowest octave tones to be facinating.
Jess, I think my favorite insertion of sax into a concert work was the alto in Ravel's Pictures at an Exhibition. I always have thought it was very interesting and quite a masterstroke that while he could've given this melody to one of the standard woods, he chose the alto, and it works *perfectly*.
The Contrabass Clarinet currently in GPO is an Eb Contrabass Clarinet made by Selmer played with a Selmer D mouthpiece.
That Eb instrument is more properly known, somewhat awkwardly, as the "contra-alto" clarinet.
A true contrabass clarinet would be most welcome, but please also add the low (written) C3 -- concert Bb1 -- to the bass clarinet as well. This is the lowest note on most modern bass clarinets, but it's inexplicably missing from the current version of GPO.