SCM drums = scm_call_1 (proc, ly_symbol2scm (instrument_string_.to_str0 ()));
audio_staff_->channel_ = (drums == SCM_BOOL_T ? 9 : -1 );
SCM drums = scm_call_1 (proc, ly_symbol2scm (instrument_string_.to_str0 ()));
audio_staff_->channel_ = (drums == SCM_BOOL_T ? 9 : -1 );