Surf music began in the early 1960s as instrumental dance music, almost always in straight 4/4 (or common) time, with a medium to fast tempo. The sound was dominated by electric guitars which were particularly characterized by the extensive use of the "wet" spring reverb that was incorporated into Fender amplifiers from 1961, which is thought to emulate the sound of the waves. Guitarists also made use of the vibrato arm on their guitar to bend the pitch of notes downward, electronic tremolo effects and rapid (alternating) tremolo picking. Guitar models favored included those made by Fender (particularly the Mustang, Jazzmaster, Jaguar and Stratocaster guitars), Mosrite, Teisco, or Danelectro, usually with single coil pickups (which had high treble in contrast to double coil humbucker picku