this predicate returns
true if the detection of musical event is simulated.
Musical event are simulated (opposed to detected by the listening machine) in fastforward mode (see @is_fastforward) and also in play mode. The play execution mode make a simulation of the normal functionning of an Antescofo program by providing a simulation of the events to detect. This mode is usefull to debug a prgram or to use the language as a kind of advanced sequencer.