this predicate returns true if the listening module is active, meaning that the system is processing an input audio stream to detect musical events specified in the score. The listening module is active in normal operation mode (launched by ::antescofo antescofo::start). The listening module is inhibited in play mode ::antescofo antescofo::play) or in fastforward mode.

See also @is_fastforward, @is_following_on, @is_paused, @is_playing_on, @is_running, and @is_stopped.