Starr Labs' Ztar is one of the few remaining guitar-like controller product lines still in production. A Ztar differs significantly from the SynthAxe and Yamaha G-10 in that the "fretboard" is covered with keys, not strings. Keys in the same row can trigger notes at the same time. This has no analog on a real guitar. It would be as if a single string were polyphonic. A number of variations are available, including an instrument that uses strings for strumming or picking, to trigger notes, whereas the pitch of the notes is determined by the keys that cover what would be a "fretboard" in an ordinary, stringed guitar. Starr labs recently introduced the Z5S, a simpler and less expensive version of the Z6S. MIDI guitar controllers have regained popularity due to the Z6 model, possibly because of its usage by Rob Swire of Pendulum, who uses it on songs where he is required to perform vocals.