The 30 July rehearsals were filmed for a short documentary titled "Music!", which was produced by the National Music Council of Great Britain. This was the first time that the Beatles had permitted a camera crew to film them developing a song in the studio. The film shows only three of the Beatles performing "Hey Jude", as George Harrison remained in the studio control room, with Martin and EMI recording engineer Ken Scott. During the rehearsals that day, Harrison and McCartney had a heated disagreement over the lead guitar part for the song. Harrison's idea was to play a guitar phrase as a response to each line of the vocal, which did not fit with McCartney's conception of the song's arrangement, and he vetoed it. Author Simon Leng views this as indicative of how Harrison was increasingly allowed little room to develop ideas on McCartney compositions, whereas he was free to create empathetic guitar parts for Lennon's songs of the period. In a 1994 interview, McCartney said, "looking back on it, I think, Okay. Well, it was bossy, but it was ballsy of me, because I could have bowed to the pressure." Ron Richards, a record producer who worked for Martin at both Parlophone and AIR Studios, said McCartney was "oblivious to anyone else's feelings in the studio", and that he was driven to making the best possible record, at almost any cost.