+ setup_refer_button (_reference, _reference_note, dcp, can_reference, cannot);
+
+ auto const ref = _reference->GetValue();
+ auto const single = sel.size() == 1;
+
+ _gain->wrapped()->Enable (!ref);
+ _gain_calculate_button->Enable (!ref && single);
+ _show->Enable (single);
+ _peak->Enable (!ref && single);
+ _delay->wrapped()->Enable (!ref);
+ _mapping->Enable (!ref && single);
+ _description->Enable (!ref && single);