Elmer is ready for bedtime, but Sylvester has other plans as he starts singing on the fence in Elmer's backyard. A series of gags play out, as Elmer tries everything up his sleeve to get rid of that unwanted pest. Elmer eventually confronts Sylvester, but before Elmer can blast him with his shotgun, Sylvester sings a sweet, gentle lullaby to ease him to dreams. However, this doesn't last, and the insanity continues…
Elmer eventually dies from explosives from his attempts to get rid of Sylvester. He winds up in Heaven, as an angel on a cloud. Momentarily he thinks he will finally get some peace and quiet. However, the spirits of Sylvester's nine lives continue to sing as they ascend around him, each with a numeral on his back (there are actually more like 18 Sylvester's depicted overall), singing the sextet from "Lucia di Lammermoor". One of them even took Elmer's halo. The exasperated Elmer dives off his cloud and a crash is heard off-screen.
The cartoon is a color remake of 1941's "Notes to You", also directed by Freleng. It has a similar plot (although the ending of the original doesn't have the characters die from an explosion; instead the cat dies from getting shot, and returns as nine singing angels), but the Elmer and Sylvester roles in "Notes to You" were taken by Porky Pig and an unnamed alley cat (the latter bearing a striking resemblance to the cat from Bob Clampett's "The Hep Cat").
"Back Alley Oproar" is notable in the Warner cartoon canon as one of the very few shorts in which Sylvester actually "wins out" over another character, albeit at the presumed cost of his life.
When this cartoon aired on the WB!, the three times Elmer runs down the steps (which are slippery from grease) and steps on tacks when trying to stop Sylvester from singing were cut.
Pop culture and musical references
Sylvester starts his concert by singing Rossini's operatic piece "Largo al factotum" from The Barber of Seville, complete with sheet music on a music stand. He is bonked by one of Elmer's shoes just as he finishes a climactic "Fiii-gaaa-rooo!"
Sylvester evokes another classical staple as he sings "la-la-la, la-la-la..." to Liszt's "Hungarian Rhapsody No. 2" while tromping in heavy boots, up and down Elmer's backstairs.
The cat sings "Some Sunday Morning" (by M.K. Jerome, Ray Heindorf and Ted Koehler) until being bonked again when Elmer throws a book titled The Thin Man at him, after which Sylvester throws a book called Return of The Thin Man at Elmer, who closes the window before the cat can finish. Then the phone rings (in a phone booth in Elmer's house), and the cat sings the final line through the phone.
Sylvester sings Jule Styne and Sammy Cahn's "You Never Know Where You're Goin' Till You Get There" (this song would be the opening music only a few weeks later in "Hop, Look and Listen").
Elmer charges after Sylvester, interrupting that number, and Sylvester hands the sheet music to a dopey-looking cat before fleeing. The cat turns the music sheet every which way, and then begins singing an excerpt from the aria, "Carissima" (by Arthur A. Penn), in a classically operatic female voice. That song comes to a sudden end when Elmer whacks her over the head, and the cat and the song both fade out like a record slowing down. Then the cat staggers and falls off the porch roof, in rhythm to the tune's closing notes.
Confronted by Elmer and his shotgun, and a threat to "bwow him to smitheweens", Sylvester sings a variation of "Brahms' Lullaby" ("Go to sleep, go to sleep, close your big bloodshot eyes...") He then carries Elmer back to his bedroom and tucks him in, still singing until he finishes. He then kisses him on the cheek sweetly and walks out the door, turning off the lights.
Seconds later, the cat jolts Elmer awake by playing a fast-paced march "Frat", by John F. Barth, another frequent WB staple, on a one-man band apparatus. Elmer chases him again, and he runs out a door and closes it. Elmer opens the door and slams his head into another door labeled "Surprize!" (sic)
Sylvester rows a rowboat across the top of the fence, singing a jazzy version of Percy Wenrich and Edward Madden's "Moonlight Bay". Elmer puts out a saucer of milk, which he has laced with alum, and summons the cat. Sylvester dances to The Sailor's Hornpipe to reach the saucer, and carefully holds a cane and straw hat out to see if Elmer has the site booby-trapped. The cat slurps down the milk, hornpipes back to his fence, and resumes singing "Moonlight Bay" until the alum shrinks his head to the size of a ping-pong ball (another oft-used WB joke), while his voice speeds up to chipmunk-level.
Sylvester apes Spike Jones with his last solo number, "Angel in Disguise" (by Paul Mann, Stefan Weiss and Kim Gannon), which also foreshadows the film's conclusion. He performs in the manner of Jones' band, starting with a brief, serious-sounding introduction (apparently not Blanc's voice), immediately seguéing into a jazzy rendition featuring a collection of crazy sound effects produced by firing guns, breaking bottles, and exploding firecrackers. As with some of the other songs in the cartoon, Sylvester sings directly to the viewing audience (see illustration). Elmer caps the performance by lighting the fuse to a box full of dynamite -- which explodes instantly and kills Elmer and Sylvester.
As Sylvester's nine-plus lives soar past Elmer, singing together like a choir, they perform part of the sextet from Donizetti's Lucia di Lammermoor, which was used in the original "Notes To You" and is also recognizable from 1946's "Book Revue" - "You can't do dis to me / I'm a citizen, see" - and from 1949's "Long-Haired Hare".
Sylvester's "Hungarian Rhapsody No. 2" was reused in Bugs Bunny's Overtures to Disaster. It used the same audio but the animation was new because Warner Brothers at the time did not have the rights to pre-August 1948 footage, although Warner still has the cartoon's original negatives stored in the vaults (the publishing rights to the music track were owned separately by Warner/Chappell Music).
The Tom and Jerry short by Chuck Jones, "The Cat Above and the Mouse Below", had a similar concept but with a different plot.
Also, this cartoon was reissued in the 1954-55 season. Since this was a Merrie Melodie, and IN TECHNICOLOR, the original end title was kept. The cartoon was shown in Blue Ribbon form from 1956-present on TV, although present-day airings air the Blue Ribbon, 1995 dubbed version, which uses the 1948 end title with a dubbed notice.