Sound delay problem

[LunaMoo]

There's no such thing like "voice delay" what you're experiencing is called input lag, this is caused not just by the software but many elements of your hardware and drivers, it's also existing in the game itself and some PSP games are known to have awful input lag even on real hardware.

Also rhythm games aren't unplayable due to input lag, that's just you as a player inability to adapt. Most people if not used to PSP timings will play those rhythm games normally because all input lag means is the fact you have to press buttons slightly faster than you would normally(and usually by max few frames which is just fraction of a second) and those games are all about keeping the rhythm not about smashing buttons as fast as you can. Rhythm can be kept easily as long as you aren't trying to play different devices with various input lag swapping between them, but that's to be expected.
Finished all patapon games and project diva long time ago on PPSSPP without any problems and to me it was much more playable on PC with full size gamepad than on real PSP where I never trully got into any of those games.

Edit: also as I always thought and still do, people who claim rhythm games are unplayable on PPSSPP probably have frame drops for example caused by texture scaling or texture replacement which causes the rhythm to change due to short freezes even if they are hardly noticeable.
We also have an option called "force real clock sync" in system settings which is something to try on, however if your hardware is too weak, it might make the problem worse.