<quote> Mine also seems to be stuck in iTunes. Sigh. <end quote>
  This is easy. 
  Make iTunes small enough to leave some of your desktop exposed. Click on the song in iTunes and (while holding down the mouse or trackpad button) drag it to the desktop. Let go. Then quit iTunes and drag the icon from the desktop to the Mail icon in the dock (postage stamp). When the Mail icon darkens and pops up the name Mail, let go of the button.
  A new mail message will open with the MP3 file attached. Address it, put in a subject (Here's the Song I'm sending you), and hit send. You're done! (This assumes you're using the native mail app on your Mac for email, not a browser-based web email portal. Though the dragging from the desktop would probably work there too. It also assumes that you own the copyright for the song; ie no DRM.)
  Hope this helps, I fix Macs for a living, and own an '89 Westy (Rocinante) for pleasure.
Allen