Billy Howerdel is an American musician and record producer. He is best known as the guitarist for the hard rock band A Perfect Circle, in which he plays alongside Maynard James Keenan. In addition to producing his own instruments and vocals, Howerdel has also produced tracks for Smashing Pumpkins, The Beta Machine, and Ashes Divide. He also sings and plays the keyboards on some of A Perfect Circle's releases. Howerdel also works as a composer for film and video game music with his past works including films such as Iron Man 2 and the video game Halo: Reach. He is also a songwriter with credits including his solo albums Gunther and Keep Telling Myself It's Alright, as well as hit singles "Medication" and "Judith".