Music in Japanese animation is often closely tied to the Japanese pop music industry, but is also a significant industry, and genre in its own right, with genre often referred to as "anison", a portmanteau of "animation" and "song", or "anime song". It is common for television and original video animation series to be accompanied by soundtrack albums, which may include the opening ("OP"), ending ("ED") and insert songs ("IN"), incidental music, original songs ("image songs") and drama tracks (short plays featuring the show's voice actors). Established Japanese musical acts often perform songs featured in animation series or movies. Likewise, it is not uncommon for voice actors ("seiyū") from anime shows to have a music career in their own right; Megumi Hayashibara, Yui Horie, Nana Mizuki,