not reach the top 60. During October that year Spectrum formed a side project, Indelible Murtceps, using the same line-up of Arnott on drums, Neale on electric piano, Putt on bass guitar and Rudd on vocals and guitar. They performed at pubs, and local dances, playing a more dance/pop-oriented repertoire and using a simpler set-up than when performing as Spectrum. Their second album, Milesago, was released in December 1971, as the first Australian rock music double album. It is also the first Australian rock album to be recorded using a 16-track recorder – newly installed – at Armstrong Studios during the previous September. McFarlane stated that it "remains one of the landmark releases of the Australian progressive rock era." It peaked at No. 9 on the Go-Set Top 20 Albums chart. By September 1972 Neale had left both bands; he was replaced by John Mills on keyboards. Neale quit the music scene permanently after leaving Spectrum and Indelible Murtceps. Spectrum's third studio album, Testimonial, was co-credited to Indelible Murtceps. It appeared in July 1973, which reached No. 12. In March, before its release, Arnott announced he was going to join Mighty Kong. Putt and Rudd decided to end both bands; each played their farewell gig at the Dallas Brooks Hall in Melbourne on 15 April 1973. It was recorded and released in December 1973 as a double live album, Terminal Buzz. Both of these releases were produced by Peter Dawkins. Spectrum had toured other Australian rock festivals, including, Wallacia (January 1971), Myponga (February), Sunbury (January 1972, January 1973), Mulwala (April 1972), and Rosebud. Their national profile was limited by a lack of radio airplay in other capitals and, other than festivals, they rarely toured outside Victoria. Ian McFarlane opined that the group were "one of the first underground bands of the early 1970s to gain mainstream acceptance. [Their] brand of progressive rock was often built around long, complex musical passages, very much in the vein of UK bands... Yet the band did embrace a commercial aesthetic at times." 1973–1999:After disbanding and reunions Following the disbandment of Spectrum and Indelible Murtceps, Rudd, Putt and Mills formed Ariel in mid-1973. The other members were Tim Gaze on guitar and Nigel Macara on drums (both ex-Tamam Shud). After Ariel disbanded in 1977, Rudd and Putt continued their musical collaborations in a series of groups: Instant Replay, Mike Rudd and the Heaters, W.H.Y., No.