An Ironically Named Song

On my way home from work today, I spent 10 minutes in the vehicle trying to remember the name of a song. I heard the melody in my head, I knew the title started with an "Un-something" and I knew Nat Cole sang it, and Natalie Cole sang it as a duet with her father's recording.

Here are the titles I kept trying but I knew were not it.

Unavoidable? (No, it's something someone wants to be.)

Undefinable? (Hmm, close, but still doesn't feel right.)

Undesirable?

Irresistible? (No, it begins with an "un-")

Finally, it came to me: Unforgettable.

Oops.