Two more things about the song "Hallelujah" which I still think coulda/shoulda been a bigger hit than it was. First off, Joshua Kreitzer corrects the date of the Tonight Show clip I posted earlier. It was May 25, 1979 (not 1976) and I have corrected the previous post.
Secondly: Here's an interesting theory as to why it didn't sell better than it did. Figuring that the names of Steve Lawrence and Eydie Gormé were not exactly "hot" with record buyers at the time, they initially released it under the names of "Parker & Penny." See that record label above? It doesn't say it's by Steve & Eydie. It says it's by Parker & Penny.
Later on, they put it on more than one album under their own names but I think that if you'd heard them perform it on Johnny's show either time in '79 and you decided you wanted to run to your local record shop and purchase a copy, they'd have told you, "Sorry, we don't have a record by that name by Steve Lawrence and Eydie Gormé!" Might that not have reduced sales somewhat? It also sounds to me a bit like the start of a Marty Feldman sketch.