In anime series, opening and ending title sequences have evolved into a distinct art form in their own right: due to the running length of a half-hour block of programming on Japanese television providing more time for the actual episode as opposed to commercials, an episode is able to budget one-and-one-half minutes each for an OP (opening sequence) and ED (ending sequence). These will invariably feature pieces of vocal music, sometimes sung by members of the voice cast for the program, and will have unique animation that thematically serves to open and close the episode; often, guest animators will be brought in to direct and provide key animation for these sequences. The OP credits will usually include director, producer, animation director, studio, music, and OP animation credits: detailed staff and voice cast is almost always reserved for the ED. In anime produced primarily for an audience of young children, karaoke lyrics to the song will sometimes be provided at the bottom of the opening and ending sequences. For further information on anime openings, see Music in Japanese animation.