The clip above is from a 1969 Elvis Presley film "Change of Habit". I'm not aware of having come across it before but the juxtaposition of the Mass going on in the traditional manner (1965 Missal, it seems) while Mr Presley gyrates to the strumming of the guitar struck me as a particularly extraordinary form of the Mass. (Although there is a continuity blip at about 3 minutes in where a lady in a blue dress from the Offertory procession seems to be assisting at the altar; perhaps some advanced liturgical experimenting already setting in?)
I found it on Mgr Pope's site Community and Mission, in a post examining the "actual" Mass endorsed by Vatican II before the modernists got their hands on moving everything along in the spirit, rather than according to what was actually mandated.
That being said, if I'd ever heard any guitar group and singers as good as this in church, perhaps I wouldn't mind so much...
... well, perhaps.