MPD as installed by Armbian needs this audio_output configuration in /etc/mpd.conf in order to use the volume control of the on-board sound with Armbian mainline kernel 5.x on the BananaPi M1 (and maybe other A20 boards):

audio_output {
    type        "alsa"
    name        "BananaPi BuiltIn"
    device        "hw:0,0"
    mixer_type      "hardware"
    mixer_device    "default"
    mixer_control    "Power Amplifier"
}

 

Update for current kernels (running linux 6.6.31 now): device and mixer_device need to change:

 

audio_output {
    type        "alsa"
    name        "BananaPi BuiltIn"
    device        "hw:1,0"
    mixer_type      "hardware"
    mixer_device    "hw:1"
    mixer_control    "Power Amplifier"
}

Or to (hopefully) protect from future renumberings:

audio_output {
    type        "alsa"
    name        "BananaPi BuiltIn"
    device        "hw:CARD=sun4icodec,DEV=0"
    mixer_type      "hardware"
    mixer_device    "hw:sun4icodec"
    mixer_control    "Power Amplifier"
}

See here for explanation of the device names to use in mpd with alsa: https://github.com/MusicPlayerDaemon/MPD/issues/374#issuecomment-432663715