From the ALSA wiki
One of the aims of ALSA is to provide full compatibility for OSS applications. ALSA has a powerful OSSEmulation which provides the following OSS devices:
- /dev/dspX (8-bit unsigned)
- also probably /dev/dspW (16-bit little-endian) and /dev/audio (logarithmic mu-law encoding; 12 or 16-bit samples crunched into 8-bit representation)
- /dev/sequencer2 (aka /dev/music)
Probably not supported:
- /dev/sndstat (human-readable status file, not intended for use by programs)
- /dev/dmfmX (raw low-level access to fm synthesizer registers)
- /dev/dmmidiX (raw low-level access to midi bus)
X is the card number from 0 to 7.
Unlike actual OSS, ALSA cannot use device files more than the assigned ones. For example, the first card cannot use /dev/dsp1 or /dev/dsp2, but only /dev/dsp0 and /dev/adsp0. In an OSS installation, symlinks without the trailing device numbers are often used to connect to devices; for example, /dev/dsp might be a symlink pointing to /dev/dsp0.
Some distributions have the device files like /dev/midi0 and /dev/midi1. These are not for OSS. They are for tclmidi, which is a totally different thing.