Things like that are to multicausal to lay at the feet of any one thing. The cassettes were important in giving people a figure to focus on, but there wouldn't have needed to be a figure if there wasn't so much dissatisfaction. If the Shah wasn't so flagrant in his profligacy, if he wasn't in power due to the US assistance, if the SAVAK weren't so brutal, etc, would people have looked for an alternative to the Shah? I would say the cassettes were more important to establishing the Ayatollah as an alternative to the Shah than being responsible for the revolution itself. I think the Shah's mismanagement was the driving reason for that. How it played out is a different story.

(For people who haven't heard about this aspect of the Revolution there were cassettes of the Ayatollah's sermons that were widely distributed throughout Iran before the revolution. One of the ironies was that the US's support of the Shah had allowed the Shah to put in a modern telephone system which allowed Khomeini to call in and deliver these sermons with enough clarity that they could be recorded, duped and distributed.)

... the revolution in Iran in 1979? I've not heard that myself, but I'd question it. Cassettes were just coming on the scene, and the Walkman was a few years in the future, so it's not like everyone had a cassette player yet.