What song...

I'm pretty sure it's just a pastiche of 60's psychedelic music written just for the movie. From what I understand, they had a very small budget for music, and they only paid for the rights to perform a tiny piece of one song-Blood Sweat and Tears'"Spinning Wheel". This was one of the 3 songs that Angela sings at the funeral-the other two, "Sometimes I Feel Like a Motherless Child" and "(Won't You Come Home) Bill Bailey" were apparently in public domain. As far as I know, everything else in the movie was composed specifically for the film. The music comming from Lance's room sounds like fairly generic 60's pop, not unlike the music comming from the radio in "Whatever Happened to Baby Jane", something written to sound like contemporary music but is simply background instrumentals. I always referred to this type of music as "muzak a'go-go", the type of music that always seemed to be playing whenever one of the Brady children on "Brady Bunch" would turn on the radio-music that bore only passing resemblance to any music of the time period.