A lot of the songs will just be GBA-ified versions of HG/SS songs (thanks to Jambo51's 12 direct sound hack). Rather than using HG/SS instruments, I'm still limiting myself to R/S/E/FR/LG instruments, because I am keeping a couple songs from the original FireRed ROM completely unchanged (such as Celadon City).
Several songs will be key-adjusted versions of their FR/LG versions, because in FR/LG they changed the keys of a lot of remixes. I want the songs to be heard in the original key that they were composed in during the 1st Generation games. For instance, in R/G/B/Y, the Vermilion City theme is in the key of A. In FR/LG, they changed it to the key of D and made it sound dumb, so I'm going to change it back to the key of A. Because I have perfect pitch (this is why I can identify key signatures so easily), this is really easy for me to do.
Some FR/LG still sound stupid no matter what key I change it to, such as the FR/LG battle theme, so I'll be composing a new R/S/E-style remix for that.
And finally, R/S/E has my favorite soundtrack. I've ported the Poke Mart theme, the "Follow Me!" theme, and the Hall of Fame room theme from R/S/E, and unlike lots of FireRed hacks, I've made it so that it sounds exactly like it does in R/S/E. I've seen FireRed hacks where people try and port songs from R/S/E and make it fit with FireRed voicegroups, which is just bad. I've ported all of the missing drum samples straight from Emerald into my FireRed ROM, and I actually make new voicegroups rather than re-using ones already in the game.
Random, but here's some more screens since there won't be any playable stuff for a while:
And some more screens of attacks:
New Hydro Pump animation
(I actually completed all of these animations back in October)