void set_range (framepos_t start, framepos_t end);
framecnt_t get_length () const { return end_frame - start_frame; }
framepos_t get_start () const { return start_frame; }
void set_range (framepos_t start, framepos_t end);
framecnt_t get_length () const { return end_frame - start_frame; }
framepos_t get_start () const { return start_frame; }