Conversation so far:
What started Steve Vai's music career in 1979?
Vai sent both a notated transcription of Frank Zappa's The Black Page, and a recording of his college band, Morning Thunder, to Zappa.
What was Frank Zappa's response to Steve Vai sending him a notated transcription?
Zappa responded by putting Vai on salary as a transcriptionist to transcribe his work.
How did Steve Vai's work progress from there?
After leaving Berklee College of Music and moving to California, Vai auditioned for and became a full-time member of Zappa's band, going on his first tour with Zappa.

Question: What instrument did he play in the band?
Self-contained rewrite: What instrument did Vai play in Frank Zappa's band?