OK. I"ve got this working but there's something strange.
The way it work is, when someone goes to my bandcamp site at domain.bandcamp.com, it gets directed to music.domain.com because of the CNAME record that I created through the DH CP.
Except that it is working differently on the two computers I'm testing it on.
On one of the computers, when I type EITHER domain.bandcamp.com OR music.domain.com, in both cases, the browser is adding a http://www in front of the url, which takes me to http://www.music.domain.com, which had been bringing up the DH quickstart.html page. This is in Firefox and IE. BUT, on another computer, on the same (home) network, the redirect works correctly and displays the redirected page from Bandcamp, as does typing music.domain.com directly in the address bar.
While testing this, I renamed the quickstart.html, so that the server wouldn't find it, and I got a Site Temporarily Unavailable page, with error id: "bad_httpd_conf". But after I changed the name back to quickstart.html, I continued getting that error, and was unable to get the quickstart page.
It seems strange that it should work on one computer but not another.
I know that there are options in the Dreamhost domain config for how to handle URLs do or do not have www as part of the URL, and I've tried different settings there. It is currently set to 'Leave it alone' and to accept both varients. But wouldn't those settings apply to all incoming requests, and thus act the same for all computers?
It's as if something is forcing the browser add the http://www to the address. But what? On the computer on which the redirect DOES work, eveb after getting to the redirected site, there is no http://www in the url, just music.domain.com/
Is there a clue in all this as to what might be happening?