Marantz PMD660 - busted capacitor!

Hello,

I've occasionally had to resolder the connections on my Marantz's headphone jack, due to the loss of one channel (the right). I think I also resoldered a small capacitor located right next to the jack, at one time. The right channel went away again at some point (my repair didn't last long), so, a few weeks ago, I disassembled the unit to fix the jack again. It appeared fine, but the little capacitor just kinda popped off the board when I bumped it. The leads were nonexistent, so I reassembled the unit until I could find a replacement cap (no luck at local electronics joints).

The unit appears to function just as it did before, with the headphone signal still coming only from the left side. My question is, can anyone ID the capacitor and tell me what it's for? If it affects the L/R signal, I definitely want to replace it. (As a sidebar, I'm not an electronics person at all, but I've wielded a soldering iron when I've needed to.)

The information on the top of the cap reads 4k 47 6.3V. Thanks so much-- it's our standard piece of equipment (been using it since 2005), and we rely on it completely for radio interviews and more.