(Lifted from the bowels of the internet)
Frank wanted to use backup singers on the songs "I'm the Slime", "Dirty Love", "Zomby Woof", "Dinah-Moe Humm" and "Montana". His road manager (at that time) suggested The Ikettes, and Ike & Tina Turner were contacted. Ike Turner insisted that Zappa pay the singers, including Tina Turner, no more than $25 per song. However, an invoice shows that they were actually paid $25 per hour, and in total $187.50 each for 7 1/2 hours of service. During the recording sessions at Bolic Sound, Tina brought Ike into the studio to hear the highly difficult middle section of "Montana" which had taken the Ikettes a few days to learn and master. Ike listened to the tape and responded "What is this shit?" before leaving the studio. Ike later insisted that Zappa not credit the Ikettes on the released album. They were (however) credited as "Debbie", "Lynn", and "Susie Glover."