"My reasons for writing pieces are often very surprising.... Two Pages, you'll recall, is a unison. Someone asked me if I was trying to follow the evolution of music history and if, then, my next piece would follow that logic and be fifths. So I wrote Music In Fifths. All movement is parallel, so I had to do one with contrary motion. After Music In Contrary Motion came its opposite, Music In Similar Motion. It was all very simple. In 1969, nobody knew me or really cared what I could write, so I could make all the jokes I wanted." - Philip Glass (in an interview with Keith Potter and Dave Smith in 1975)

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.