I HAD a spectacular John Cage moment on an uptown A train recently.

You know about Cage moments, don’t you? We all have them, whether we think of them that way or not. They occur when happenstance kicks in, and surprising musical experiences take form, seemingly out of nowhere. They can happen anywhere at any time. This year, thanks to the Cage centenary, official Cage moments have been plentiful, with performers of all stripes — students at the Juilliard School; ensembles like So Percussion, Iktus Percussion and the pianist Taka Kigawa, and the Flux Quartet and friends — inducing them through spirited renditions of Cage’s music.

But the unofficial moments are the ones to wait for. My earlier favorite Cage moment occurred just over a year ago, when I sprained an ankle and had an M.R.I. The technicians warned me that I might find the noise annoying, but as it turned out, I couldn’t help focusing on the machine’s repeating rhythmic patterns, pitches and changing overtones. I thoroughly enjoyed it, although in truth I found the M.R.I.’s music closer to early Philip Glass than to Cage.

On the A train I wasn’t thinking about Cage at all. I had just heard an exquisitely turned, energetic performance of Schubert’s String Quintet in C at a church in Greenwich Village, and Cage could not have been further from my thoughts. Nor did the crowded subway car bring him to mind at first. But I noticed that it was unusually noisy.

Typically, most of the noise you hear comes from the subway itself: its din drowns out conversations, and people tend to stare at their feet, or at whatever they are reading, and listen to their portable music players. But this Tuesday evening just about all the people were talking, and working hard to drown out both the subway and the chats taking place around them.