(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 ****?" 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."