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.