ags_sequencer_editor_callbacks
void ags_sequencer_editor_backend_changed_callback (GtkComboBox *combo, AgsSequencerEditor *sequencer_editor);
GtkComboBox *combo
AgsSequencerEditor *sequencer_editor
void ags_sequencer_editor_card_changed_callback (GtkComboBox *combo, AgsSequencerEditor *sequencer_editor);