(I have 2 emulators of choice on my phone -- VGBA which runs slow and has several bugs, and gpSP which seems to run better than VBA does on my computer lol)
I can try to get a screenrecord of a short play which shows a soundtrack that I find sounding wrong, which sound OK on my computer, so you can compare it with the PSP version of gpSP to see if they sound the same.
What phone are you using, by the way? If it has at least a 1GHz processor, I'd suggest checking out GBA.emu on the Play Store. It's by a well-regarded emulator developer and it's based right off of one of the newest versions of VBA-M, so you can rely on it for good performance. Othewise I don't know what to tell ya, a lot of GBA emulators don't account for proper GB Synth emulation until later into development. This is especially true for GBA emulators made for portable devices.