From The Three Stooges Journal # 92 Winter 1999, (http://threestooges.net/journal.php?action=view&id=92), from the article "Curly Cues: More Stooge Short Music Identified" by Richard Finegan...
Brazilian Cotillion, composed by Robert Wright and Chester Forrest for the Columbia feature BLONDIE GOES LATIN (1942). Brief snippet of it heard earlier in the Buster Keaton short SHE'S OIL MINE (1941), later used again in 1942 in BLONDIE FOR VICTORY.
That's not surprising, since it's completely in line with Columbia's policy of using either public domain music or music by in-house composers, in order to avoid paying royalties to music publishers or getting in trouble with ASCAP. For example, in "Punch Drunks," the original idea was to use a John Philip Sousa march as the tune that makes Curly go berserk. However, Sousa had only recently died (in 1932) and his music was still under copyright, so they went with "Pop Goes The Weasel" instead.
Which turned out to be an inspired choice— I can't think of
any Sousa composition or any other song, period, that would have been funnier or more appropriate. In my mind (and those of a lot of other Stooges fans, I'm sure), "that Weasel tune" will be forever identified with Curly Howard.
The Keaton shorts use "Merrily We Roll Along" as the opening theme; once more, music that wasn't new or under copyright, but it works just fine.
