A Linux audio mixing/etc/asound. conf configuration.

Backup.
Only the same user can enable the device simultaneously.

PCM .! Dmix {
Type dmix
Ipc_key 5678293
Ipc_key_add_uid Yes
Slave {
PCM "HW: 0, 0"
Period_time 0
Period_size 2048
Buffer_size 16384
Format s16_le
Rate 48000
}
}
PCM .! Dsnoop {
Type dsnoop
Ipc_key 5778293
Ipc_key_add_uid Yes
Slave {
PCM "HW: 0, 0"
Period_time 0
Period_size 2048
Buffer_size 16384
Format s16_le
Rate 48000
}
}

PCM. asymed {
Type asym
Playback. PCM "dmix"
Capture. PCM "dsnoop"
}

PCM .! Default {
Type plug
Slave. PCM "asymed"
}

PCM. dsp0 {
Type plug
Slave. PCM "asymed"
}

CTL. mixer0 {
Type HW
Card 0
}