typedef void (*apply_gain_to_buffer_t) (ARDOUR::Sample *, pframes_t, float);
typedef void (*mix_buffers_with_gain_t) (ARDOUR::Sample *, const ARDOUR::Sample *, pframes_t, float);
typedef void (*mix_buffers_no_gain_t) (ARDOUR::Sample *, const ARDOUR::Sample *, pframes_t);
typedef void (*apply_gain_to_buffer_t) (ARDOUR::Sample *, pframes_t, float);
typedef void (*mix_buffers_with_gain_t) (ARDOUR::Sample *, const ARDOUR::Sample *, pframes_t, float);
typedef void (*mix_buffers_no_gain_t) (ARDOUR::Sample *, const ARDOUR::Sample *, pframes_t);