Unfortunately, it doesn't works, even using 3 players for each song (as buffers), with 128 of framecount. It keeps coming out of sync, with intervals of 100 - 125 miliseconds.
The stranger thing is that even creating a new player for each song (with the same id used) in every OnTimer execution, it was perfectly synchronized (with uos_Play). But, with uos_PlayNoFree, that mess happens. But it's probably not just a UOS problem, since I saw similary issue in tests with SDL and SDL Mixer.
But, using uos_Play, occurs a gradual increase in memory... It looks the function didn't actually free the player after the sound was stopped. I noticed this in the task manager (Windows 10, 64-bit). Maybe a bug?
Thanks for your attention e dedication, Fred.