This is an interesting arrangement which sets off both Bix's solo and Bing's vocal beautifully. I've got photocopies of the band parts from the Whiteman Collection at Williams College (Williamstown, Mass.) and what's striking is how different the parts are from the three extant recordings. It looks like the vocal trio parts were not always part of the band's live performances as the "a tempo" section just before Bix's solo (which is "scat sung" by the Rhythm Boys on the recording) is scored for trombones and saxes-maybe for performances without the Rhythm Boys. As well, the form of the arrangement (according to the band parts) includes a stop-time chorus where the band members stomped their feet in between snatches of the melody played by the winds and brass. The violin section soli on the recording ( and contained on the parts) was essentially a harmonization of the verse of the song-which can be heard (with lyrics) on the Rhythm Boys version of "From Monday On". The brass soli which follows the violin section feature is also in the parts but comparing the lead cornet line (played by Bix) with the 3 recorded takes we have on this piece, Bix took some liberties with the written line (not surprisingly!). You're right that this section resembles "Clarinet Marmalade" and "San" as Matty Malneck either composed a soli for the brass in Bix's style or got together with Bix (as Bill Challis often did) and transcribed a solo as played by Bix, afterwards harmonizing it for a section of instruments. Too bad that the Frank Trumbauer version of "From Monday On" is lost to us. It would be interesting to have it around for comparison!