Is easy (thanks to sevitz.com), except that you need Rendezvous Proxy on the system where you will actually be listening to the music (not the machine where the music normally resides). iTunes uses port 3689, so you must setup an SSH tunnel:
too-quiet$ ssh -L 3689:localhost:3689 user@lotsa-music
Now, run Rendezvous Proxy on ‘too-quiet’, Add Host, use 127.0.0.1 for IP address, 3689 for port, and type a name for Host Label. iTunes will initially see your shared music library as this name, but will update with the “real” name shortly thereafter. Service Type – _daap._tcp. (iTunes Host).
I wish I’d realized how straightforward this is long ago. My next wish is to “tunnel USB” so that I can sync my iPod from a far-away land.