being sand cast, with early versions having an attached string mute beneath the bridge (much like the Fender Jaguar) and a rather short handle. This he called the "Vibramute". Two years later, he slightly simplified the design, going to a die cast design, eliminating the mute (which more players complained about than favored) and lengthening the vibrato arm slightly. This incarnation, called the "Moseley", was used on all Mosrite guitars from that point on. The actual feel and response of the two different models is virtually identical, however. Moseley also designed a companion 12-string vibrato for the 12-string version of the instrument, and this may have been one of the only – if not the only – vibratos designed for use on a 12-string guitar. Locking tremolo Floyd Rose Around 1979, Floyd D. Rose invented the locking tremolo. This vibrato system became highly popular among 1980s heavy metal guitarists due to its tuning stability and wide range of pitch variation. The original Floyd Rose system was similar to the Fender synchronized tremolo, but with a number of extra mechanisms. The first and most obvious is a locking plate on the head nut, tightened with a hex key that fixes the strings at this point after tuning. This provides extra tuning stability, particularly while using the vibrato arm—but it also prevents tuning with the machine heads. Fine tuners have been provided as part of the bridge mechanism on all but the earliest units to allow minor retuning without unlocking the nut. It is rumored, but has never been confirmed that Eddie Van Halen had a part in the inclusion of the fine tuning unit. In a 1982 Guitar World interview for Van Halen's Diver Down album, Eddie claimed that he co-invented the fine tuners. Nonetheless, a gift of a unit to Van Halen by Floyd Rose himself gave the unit instant overnight success and credibility. Still more stability was provided by the addition of a second lock on the bridge nut, making a double locking tremolo system that was more complex to set up. The double locking design is sometimes called a two-point locking tremolo, inviting confusion with the Fender two-point synchronized tremolo, which is a different concept and not a locking tremolo at all. Many guitars equipped with locking tremolo systems have a cavity routed in the body beneath and behind the bridge, extending the range of motion, a concept