Details: Here's the joke pushed to eight pipers: four bagpipes, four bombards. These "first classics" are the premise for Einstein on the Beach. Philip Glass composed them after a trip to North Africa and India. Perhaps that's why these pieces are modal and perfectly suited to bagpipes? Surprisingly, they seem to have been written for our instruments. - "My reasons for writing pieces are often very strange... Two Pages, you remember, is in unison. Someone asked me if I was attempting to trace the progress of musical history and if, therefore, my next piece would follow on logically and be in fifths. So, I wrote Music In Fifths. That was all in parallel motion, so I obviously had to do one in contrary motion next. And after Music In Contrary Motion came it's opposite again, Music In Similar Motion. It was a very easy-going thing. In 1969, nobody knew me or really cared much what I wrote, so I could make any jokes I liked." Philip Glass (in an interview with Keith Potter and Dave Smith in 1975)