Who sang the Cheers theme song?

The file

Portnoy and Angelo had written a song for a Broadway show that got cut; the Cheers producers heard it and asked for a rewrite about a bar. The rewrite is the one that's still played at every retirement party.

The full song has verses nobody knows, because the show only ever used the chorus. Portnoy sang it himself, over sepia photographs of old bars, for eleven seasons.

Sources: Wikipedia — Where Everybody Knows Your Name