Oh, thanks I misunderstood that part of documentation.
EDIT: That does not explain crash, though, so I would still like to get some response on that. Was I using API in the wrong way?
Also, there is a problem with al_play_sample, because you can't do anything with it after it has been started. It seems strange to me. I have SAMPLE_ID. I can stop it. Shouldn't I be able to adjust its gain, at least? Or is there any architectural problems which prevent me from doing this?
EDIT2: OK, I have found what led to crash. I was loading the same file into two different ALLEGRO_SAMPLEs, then creating an INSTANCE of each and trying to play them. While I still don't understand why should this crash library, now at least I can avoid this crash.