A short explanation of what happens in the /etc/modules.conf file
From the ALSA wiki
After the main multiplexer is loaded, its code requests top level sound card module. String snd-card-%i is requested for native devices where %i is sound card number from zero to seven. String sound-slot-%i is requested for native devices where %i is slot number for ALSA owner this means sound card number. The options line allows you to set various config options before the module is loaded. String snd_id lets you set the name of the card which is returned in the /proc/asound/cards file. Other options may be available which are card specific. The options for these are found in the INSTALL file or above.
# ALSA portion alias snd-card-0 snd-interwave alias snd-card-1 snd-cmipci options snd-cmipci id="first" enable_midi="1" # OSS/Free portion alias sound-slot-0 snd-card-0 alias sound-slot-1 snd-card-1
NB. For drivers older than 0.9.0rc5 use:
options snd-cmipci snd_id="first" snd_enable_midi="1"
The "snd_" prefix has been removed from the "module options" to fit with the kernel standard.
Autoloading OSS/free emulation
We are finished at this point with the configuration for ALSA native devices, but you may also need autoloading for ALSA add-on OSS/Free emulation modules. At this time only one module does not depend on any others, thus must be loaded separately, snd-pcm1-oss.o. String sound-service-%i-%i is requested for OSS/Free service where first %i means slot number e.g. card number and second %i means service number.
# OSS/Free portion - card #1 alias sound-slot-0 snd-card-0 alias sound-service-0-0 snd-mixer-oss alias sound-service-0-1 snd-seq-oss alias sound-service-0-3 snd-pcm-oss alias sound-service-0-8 snd-seq-oss alias sound-service-0-12 snd-pcm-oss # OSS/Free portion - card #2 (cmipci) alias sound-slot-1 snd-card-1 alias sound-service-1-0 snd-mixer-oss alias sound-service-1-3 snd-pcm-oss alias sound-service-1-12 snd-pcm-oss
The alias for snd-seq-oss is not necessary on the second device, because there is only one /dev/sequencer, regardless how many devices you have.