CONFIG_SND_SYNTH_EMUX (not configurable)

modulename: snd-emux-synth.ko

configname: CONFIG_SND_SYNTH_EMUX

Linux Kernel Configuration
└─>Device Drivers
└─>Sound card support
└─>Advanced Linux Sound Architecture
└─>SND_SYNTH_EMUX
In linux kernel since version 3.10 (release Date: 2013-06-30)  
source code:
sound/synth//emux/