Beatles legend played to just 300 people at a roadhouse venue close to the Desert Trip festival site
Both artists headlined the second night of the California mini-festival
The Beatle also apparently danced with the US Presidential candidate at the event in the Hamptons
The pair met in Cleveland before the Beatle's concert on Wednesday (August 17)
Beatles legend collaborated with the rapper on three tracks that came out in late 2014 and early 2015
McCartney also discusses his relationship with Yoko Ono and reuniting with Ringo Starr
Pair played 'Helter Skelter' and 'Hi Hi Hi' in Boston
"Dear Princely person," McCartney wrote in the note
Photo was taken at AIR Studios in Montserrat, thought to be during 1981