Тем временем в MASTER ветке ПшПшАудио:
$ grep -rnw ./pulseaudio -e slave
./pulseaudio/src/modules/module-combine-sink.c:56:        "slaves=<slave sinks> "
./pulseaudio/src/modules/module-combine-sink.c:1205:        /* Check if the sink is a previously unlinked slave (non-automatic mode) */
./pulseaudio/src/modules/module-combine-sink.c:1351:    /* Check the specified slave sinks for sample_spec and channel_map to use for the combined sink */
./pulseaudio/src/modules/module-combine-sink.c:1365:                pa_log("Invalid slave sink '%s'", n);
./pulseaudio/src/modules/module-combine-sink.c:1469:                pa_log("Invalid slave sink '%s'", n);
./pulseaudio/src/modules/module-combine-sink.c:1477:                pa_log("Failed to create slave sink input on sink '%s'.", slave_sink->name);
./pulseaudio/src/modules/module-combine-sink.c:1483:            pa_log_warn("No slave sinks specified.");