21-fret necks. There was also a glued-in "set neck" 4000 version in 1975-76 (neck set like a Gibson Les Paul), which featured a 20-fret neck, dot inlays, no binding (similar to the 4001S) and only a single bridge-position mono pickup. Fred Turner of Bachman-Turner Overdrive used the 4000 extensively on the Not Fragile album, as seen in a promotional clip for "You Ain't Seen Nothing Yet." This bass also appears on the gatefold sleeve of Four Wheel Drive. In the 1970s, the Rickenbacker bass became a staple of progressive rock, as exemplified by British bassists Mike Rutherford (Genesis) and Chris Squire (Yes). Squire was one of the first to supercharge the 4001 by splitting the signal, sending the neck pickup output to a bass amp and the bridge pickup output to a lead guitar amp. Combined with his aggressive picking technique on Rotosound roundwound strings, the effect was a growling, grinding, "concrete mixer" tone that continues to be admired and emulated. In the hard rock vein, Deep Purple's Roger Glover was a prominent Rickenbacker aficionado. Geddy Lee of Rush used a Rickenbacker on the band's earlier material. Another enthusiast was Metallica bassist Cliff Burton, whose heavily modified 4001, red with white hardware and trim, debuted during the group's Kill 'Em All era. Also noteworthy was Motörhead vocalist/bassist Ian "Lemmy" Kilmister, for whom Rickenbacker produced a 60-bass run of "Lemmy Kilmister" signature basses: the 4004LK, fitted with three pickups, gold hardware, and elaborate wood carving in the shape of oak leaves. In 2019, the company produced a 420-bass run of Al Cisneros signature basses honoring the prominent Sleep and Om bassist, a long-time Rickenbacker proponent. Cisneros's 4003AC model features a signature pickguard, green inlays on the fingerboard, and a removable thumb rest. The sound of Rickenbacker basses featured early on in the UK punk/New wave music explosion of the late 1970s and early 80s and was used by: Glen Matlock (Sex Pistols), Paul Simonon (The Clash), Peter Hook (Joy Division), Bruce Foxton (The Jam), Paul Gray (The Damned, Eddie & the Hot Rods), Tony James (Generation X), Mike Mills (R.E.M.), Michael Bradley (The Undertones), Youth (Killing Joke) and in the U.S., Kira Roessler (Black Flag). Brazilian bassist Alex Malheiros from Azymuth used a 4001 bass during the band's early years (most notably between 1972 and 1977). His very rich approach to samba, jazz and funk has some echoes of Chris Squire