CONFIG_SND_OPL3_LIB_SEQ (not configurable)

modulename: snd-seq-midi-event.ko

and/or

snd-opl3-synth.ko

configname: CONFIG_SND_OPL3_LIB_SEQ

Linux Kernel Configuration
└─>Device Drivers
└─>Sound card support
└─>Advanced Linux Sound Architecture
└─>SND_OPL3_LIB_SEQ
In linux kernel since version 2.6.31 (release Date: 2009-09-09)  
source code:
sound/core//seq/