Digging deeper, I found a version of "It Must Be Jelly (Cause Jam Don't Shake Like That)" that predates Frankie "Half Pint" Jaxon's version for more than 18 months and has a title much nearer to Glenn Miller's recording: "It Must Be Jelly ('Cause Jam Don't Shake That Way)" by The Hipp Cats, recorded on August 13, 1938 and released around October 1938 on Decca 7518. Like Jaxon's version it is more explicit than Miller's, if you know what "jelly-roll" was generally used for in black slang. Interestingly, the record label shows the song as composed by Harold Boyce, whereas the Glenn Miller record shows "George Williams-J.C. MacGregor" as composers and Woody Herman's 1944 record shows "MacGregor-J. Chalmers-Sunny Skylar." See also vocalgroupharmony.com
And the sheet music cover {Image #642221} had to have been printed before late 1945, because it was then that Sixth Avenue in midtown Manhattan ("New York 20, N.Y.") was rebranded with the more snazzy-sounding "Avenue of the Americas."
The actual studio recordings of "It Must Be Jelly" and "Rainbow Rhapsody" The video provided below by Fixbutte was sourced from a September 15, 1942 broadcast of Miller's Chesterfield show which aired from the RKO Keith's Boston Theater, Boston, MA between 7:15 - 7:30 p. m.
Looking for Frankie "Half-Pint"Jaxon's original recording I had linked a tiny sound clip from AMG at first (mistitled like the Glenn Miller song there, but Jaxon actually sings, "It must be jelly, 'cause you know jam don't shake"). However, we don't need it anymore as the full recording of Frankie "Half-Pint" Jaxon is also on YouTube:
As already said, the refrain is nearly identical - and the whole thing is swinging and excellently played.
Indeed, the relationship between this recording and Carl Perkins' "Gone, Gone, Gone" is obvious: "Well that must be my girl, yours don't look like that ..."
Interesting. Frankie "Half-Pint" Jaxon was a female impersonator (famous for the song "Fan It", beloved of later Western-Swing bands). The song had a re-surgence in 1955, when Sun records issued a Rockabilly version by Carl Perkins entitled "Gone Gone Gone".
One last word on the lapidary lyrics. As presented on a lyrics site, composer/arranger George "The Fox" Williams, with his New Orleans origin, was apparently inspired by a recording of an African-American musician, Frankie "Half Pint" Jaxon, whose "You Know Jam Don't Shake" (Decca 7733, recorded March 5, 1940), contains the lines, "It must be jelly, 'cause you know jam don't shake, / Yas, yas, she's got what it takes."
The studio version of "It Must Be Jelly" is about three minutes long (3:01). Flower's discography lists the following soloists:
piano, MacGregor; tenor sax, Klink; trumpet, Best; trumpet, May; alto sax, Martin; drums, Purtill
The Modernaires were a vocal group then consisting of Ralph Brewster, Bill Conway, Hal Dickinson, Chuck Goldstein, and (as a non-permanent member) Paula Kelly.
The full lyrics go: "It must be jelly 'cause jam don't shake like that / Oh Mama, you're so big and fat!". As the record label shows, music and lyrics are credited to pianist J. C. "Chummy" MacGregor and arranger George Williams. As some sources give Sunny Skylar as lyricist, this may relate to an expanded set of verses, as recorded by Woody Herman in 1944.
Here's a YouTube clip of "It Must Be Jelly", but apparently from a later broadcast performance (see there - possibly Captain Glenn Miller on the October 16, 1943 I Sustain the Wings radio program on NBC radio with the AAF Training Command Band featuring Ray McKinley):
This record contains two of 13 tracks recorded on a three-day session (14-16 July 1942) in Chicago that proved to be the very last recording session of Glenn Miller's civilian band. Here's a lot of further information about the session, taken from John Flower's MOONLIGHT SERENADE: A Bio-discography of the Glenn Miller Civilian Band (only slightly edited by me).
"Personnel Trombones: Glenn Miller, Jimmy Priddy, Paul Tanner, Frank D’Annolfo Trumpets: Billy May, Steve Lipkins, Dale McMickle, Johnny Best Reeds: Lloyd “Skippy” Martin, as; Ernie Caceres, as, bar & clt; Wilbur Schwartz, clt & as; Tex Beneke, ts; Al Klink, ts Rhythm: Chummy MacGregor, p; Bobby Hackett, g; Doc Goldberg, b; Maurice Purtill, d
14 July, 1942 (TUE): Victor Studios, Chicago, Illinois
074736-1 Victor [Vi] 27953-A Dearly Beloved (arr Jerry Gray [JG]) - voc Skip Nelson (and Chorus)
From the Columbia film “You Were Never Lovelier”
(Johnny Mercer-Jerome Kern)
074737-1 Vi 20-1520-B Moonlight Mood (arr JG) - voc Skip Nelson and The Modernaires
(Harold Adamson-Peter De Rose)
074738-1 Vi 20-1536-B Caribbean Clipper (arr JG)
(Jerry Gray)
074739-1 Vi 20-1563-A Here We Go Again (arr JG)
(Jerry Gray)
All tunes 1 take. (RCA Victor)
This session lasted from 11:00 am to 2:40 pm. (RCA Victor)
15 July, 1942 (WED): Victor Studios, Chicago, Illinois
074740-1 Vi 20-1523-A That Old Black Magic - voc Skip Nelson and The Modernaires
From the Paramount film “Star Spangled Rhythm”
(Johnny Mercer-Harold Arlen)
074741-1 Vi 20-1520-A Moonlight Becomes You - voc Skip Nelson and The Modernaires
From the Paramount film “Road to Morocco”
(Johnny Burke-Jimmy Van Heusen)
074742-1 Vi 20-1509-A Juke Box Saturday Night (arr JG) - voc Marion Hutton, Tex Beneke and The Modernaires
From the musical production “Stars on Ice”
(Albert Stillman-Paul McGrane)
074743-1 Vi 20-1546-A It Must Be Jelly (‘Cause Jam Don’t Shake Like That) (arr George Williams) - voc The Modernaires
(George Williams-John Chalmers MacGregor)
That Old Black Magic 2 takes; all other tunes 1 take. (RCA Victor)
This session lasted from 11:00 am to 3:15 pm. (RCA Victor)
Victor almost did not release Juke Box Saturday Night because of possible offense to coin machine operators. (DB, Sept. 15, 1942) Ralph Brewster did both of the Ink Spots’ imitations with Hal Dickinson singing the high voice when Brewster was singing the deep voice. Bill Conway arranged the harmony.
16 July, 1942 (THU): Victor Studios, Chicago, Illinois
074744-1 Vi 27953-B I’m Old Fashioned - voc Skip Nelson
From the Columbia film “You Were Never Lovelier”
(Johnny Mercer-Jerome Kern)
075745-1 Vi 20-1523-B A Pink Cocktail for a Blue Lady (arr JG) - voc Skip Nelson
(Herb Magidson-Ben Oakland)
074746-1 Vi 20-1546-B Rainbow Rhapsody
(Benny Carter)
074747-1 Vi 20-1509-B Sleepy Town Train
(Allan Roberts-Bill Fontaine)
074748-1 Vi 20-1529-A Rhapsody in Blue (arr Bill Finegan)
(George Gershwin)
All tunes 1 take. (RCA Victor)
This session lasted from 11:00 am to 3:45 pm. (RCA Victor)
This was the last recording session by the Miller civilian band due to the dispute between the American Federation of Musicians and the recording companies. A ban on recording was imposed by the Union on its members as of August 1, 1942, and this continued until November 22, 1944 for RCA Victor and Columbia. Decca and several other new companies began recording in October of 1943. Since Miller was well aware of this upcoming ban on recording, the above “slew” of recordings over a three day period was the result. Some of these tunes were released by Victor as late as January, 1944." *
_____________________
* Actually the last record from the session was Here We Go Again (b/w Long Time No See, Baby) on Victor 20-1563 which was released in the first week of March 1944.
Both sides were recorded on July 15, 1942 (shortly before the first musicians union recording ban) but not released before December 1943 (advertised as a new record in Billboard of Dec 11, 1943, p. 67). The A side title, relating to a woman with curves, was so much jive talk that it even made Billboard's Harlem Hit Parade (#2 on Feb 19, 1944).