Well, the Game Gear sound chip is essentially a modified version of the SMS sound chip. The main difference is hard stereo panning.

VGM Music Maker is a good option for stereo game gear music making. Just export to a .GG file. You can also export a .vgm file and convert to a ROM.

I wish Deflemask supported sampling and stereo support for the PSG. But so far that has not happened.

I made a post somewhere here asking about the state of Game Gear music trackers or possible software.  Maybe you can dig it up.  iirc the answers were not promising basically because of un-uniqueness of the soundchip and the lack of interested developers.

Would also like some info on this as well.

Hello! My friend gave me his Game Gear. I've been looking around at music possibilities and I have a few questions; as I understand it, my main option for actually using a Game Gear is to:

-write in Deflemask under Sega Master System
-export songs to ROMs
-buy an everdrive cart, flash all of the song ROMs to the everdrive
-???

I'm coming from almost exclusively an LSDJ background so a lot of what I've read about using this and other older systems is hard to understand, not to mention less information, tutorials, etc. available

I think I read that the pulse channels can also handle audio samples, is that correct? Will Deflemask handle that while writing for SMS?
I noticed some other trackers, (sneven tracker, Little Scale's program, mod2psg2) and they all look like a more comfortable interface but Deflemask seems like the only finished program that I can use to get my songs on to hardware. Is that true?
Is there any other advice I should know for starting out?
I greatly appreciate any help!