"And a voice from you and me"
This is referring to Bob Dylan playing "Blowin' in the Wind," but doesn't have the best singing voice.
"The courtroom was adjourned, no verdict was returned"
Lee Harvey Oswald was never convicted of the Kennedy assassination because he was murdered.
"And we sang dirges in the dark, the day the music died"
The dirges (funeral songs) were for the Kennedy's and Martin Luther King, being they both died in the mid 60's.