Yes.
You wil need to use the file attachment feature of your email program. Every program is different, so it's impossible to be more specific without knowing what you normally use to send emails. Look for something along the lines of "attach file" or "file attachment".
Note: If it's hotmail or a similar web based email account then they will probably have a size limit on what you can send. I think hotmail limits to 1 Meg which is much smaller than a typical mp3 file, so you will not be able to send an mp3 file with this type of email system.
-Kev