ALSA can't set periods

I've posted this before, but it seems to have disappeared after I edited the link back in, so I'm trying it again; sorry if this winds up as a duplicate.

When starting up Musescore on Gentoo, the playback buttons are disabled and I get the following error in the console:
Alsa_driver: can't set periods to 3.
init ALSA audio driver failed
init ALSA driver failed
no audio driver found
Cannot start I/O
sequencer init failed

I'm sure it's an issue with my own ALSA setup rather than being a problem with MuseScore itself, but since the message is printed from MS code, I figured someone here would have a better idea of what exactly's wrong with it.