VGBA-Android 4.3, a new version of my GameBoy Advance emulator released today, comes with major sound quality improvements:

https://play.google.com/store/apps/details?id=com.fms.vgba

Many users complained about VGBA sound quality in the past. In the new VGBA release, I have switched to a different sound rendering algorithm, finally fixing the delay between direct and melodic audio channels that many Pokemon Fire Red and Leaf Green users had problems with. The problem was not limited to Pokemon, so other affected games will show improvement as well. In addition to fixing the delay issue, the new sound code also removes echo and distortions. A few game-specific audio problems may still occur though.

• Switched to simpler and more precise sound rendering algorithm.
  
• Fixed lag between wave and melodic channels (Pokemon games, etc).
  
• Improved overall audio quality a lot.