/* What we really want to do here is what Editor::fork_region()
does via Session::create_midi_source_by_stealing_name(), but we
don't have a Track. We'll just live with the skipped number,
/* What we really want to do here is what Editor::fork_region()
does via Session::create_midi_source_by_stealing_name(), but we
don't have a Track. We'll just live with the skipped number,