I bet there’s an open source version and a Mac port

Terrific sentence in an Alex Ross article about Philip Glass’ most recent works:

At times, it seems as though [Glass] had launched Microsoft Arpeggio on a computer and gone off to have tea with, say, Richard Gere.

I would have thought Glass would use iArpeggio on a Mac, but then I realized I was mixing it up with iPulse, which I imagine Steve Reich uses. The rest of us could probably use the free versions: OpenArp and ChugChug.