Advanced Linux Sound Architecture (ALSA) project homepage
Alsa Opensrc Org

Using ffmpeg (for most audio formats):

SDL_AUDIODRIVER="alsa" AUDIODEV="hw:0,0" ffplay -nodisp audiofile.flac

Source:Super User - select ffplay audio out device

Using mpg123 (for mp3's only):

mpg123 -a hw:1,0 audiofile.mp3

For example, to dump the hardware parameters for a Digidesign MBOX 2:

arecord --dump-hw-params -D hw:M2,0

Recording WAVE 'stdin' : Unsigned 8 bit, Rate 8000 Hz, Mono
HW Params of device "hw:M2,0":
--------------------
ACCESS:  MMAP_INTERLEAVED RW_INTERLEAVED
FORMAT:  S24_3BE
SUBFORMAT:  STD
SAMPLE_BITS: 24
FRAME_BITS: 48
CHANNELS: 2
RATE: 48000
PERIOD_TIME: [1000 1820438)
PERIOD_SIZE: [48 87381]
PERIOD_BYTES: [288 524286]
PERIODS: [2 1024]
BUFFER_TIME: [2000 3640875]
BUFFER_SIZE: [96 174762]
BUFFER_BYTES: [576 1048572]
TICK_TIME: ALL
--------------------
arecord: set_params:1297: Sample format non available
Available formats:
- S24_3BE

Here you can see the MBOX2 only supports the S24_3BE (signed 24-bit 3bytes Big Endian) format.

Source:SourceForge - ALSA - Mailing Lists - Re: [Alsa-user] arecord: begin_wave:2480: Wave doesn't support S24_3BE format

Get a list of midi devices:

aplaymidi -l

Example output:

 Port    Client name                      Port name
 14:0    Midi Through                     Midi Through Port-0
 20:0    USB Midi                         USB Midi MIDI 1
 44:0    Mbox 2                           Mbox 2 MIDI 1
 48:0    Mbox 2                           Mbox 2 MIDI 1

To use the midi device named “USB Midi” on port 20:0 in above output in DOSbox, edit the [midi] part in your DOSbox config in ~/.dosbox/dosbox-VERSION.conf (in my case ~/.dosbox/dosbox-0.74-3.conf) to look like this:

[midi]
#     mpu401: Type of MPU-401 to emulate.
#             Possible values: intelligent, uart, none.
# mididevice: Device that will receive the MIDI data from MPU-401.
#             Possible values: default, win32, alsa, oss, coreaudio, coremidi, none.
# midiconfig: Special configuration options for the device driver. This is usually the id of the device you wan
t to use.
#               See the README/Manual for more details.

mpu401=intelligent
mididevice=default
midiconfig=20:0

Show all soundcards that are recognised by ALSA:

aplay -l | grep card

Test playback on a specific card:

speaker-test -c2 -twav -Dhw:Creative

Test playback on a specific pcm or dmix device definied in a manually edited .asoundrc:

speaker-test -c2 -twav -Ddmixsoundblasterz

This helps to track down vague error messages in a .asoundrc that sends sound output to multiple soundcards simultaneously.

For faking a 7.1 channel setup on a stereo soundcard.

Save the below code to ~/.asoundrc and change the pcm.maudiomicrodac part to match your card (see 'aplay -l | grep card' output):

pcm.!default {
        type asym
        playback.pcm "plug:stereo2quad"
}

pcm.dmixer  {
        type dmix
        ipc_key 1024
        slave {
                pcm "maudiomicrodac"
                period_time 0
                period_size 1024
                buffer_size 4096
                rate 48000
        }
        bindings {
                0 0
                1 1
                2 0
                3 1
                4 0
                5 1
                6 0
                7 1
        }
}

pcm.stereo2quad {
        type route
        slave.pcm "dmixer"
        ttable.0.0 1
        ttable.1.1 1
        ttable.2.2 1
        ttable.3.3 1
        ttable.4.4 1
        ttable.4.5 1
        ttable.5.4 1
        ttable.5.5 1
        ttable.6.6 1
        ttable.7.7 1
}

pcm.maudiomicrodac {
        type hw
        card DAC
        device 0
        channels 2
}

ctl.dmixer {
        type hw
        card 0
}

Sources:

• bootlin - Audio multi-channel routing and mixing using alsalib
• unix stackexchange - Splitting the outputs of a 7.1 USB sound card into 4 distinct stereo pairs
• askubuntu - How to split 7.1 soundcard outputs to 4 stereo outs with ALSA
• AlsaProject - Asoundrc
• AlsaProject - PCM (digital audio) plugins PCM plugins extends functionality and features of PCM devices. The plugins take care about various sample conversions, sample copying among channels and so on.