Thanks for the replies. "When the band begins to play" is a catch phrase from around 1900. I was wondering if this and "Whoa Mule" were of minstrel origin?

Notice the floating lyrics are found in many songs today, esp. "Whoa
Mule"

Here's some info from 1911:

THE JOURNAL OF AMERICAN FOLK-LORE Vol. XXIV. —JULY-SEPTEMBER, 1911— No. XCIII

FOLK-SONG AND FOLK-POETRY AS FOUND IN THE
SECULAR SONGS OF THE SOUTHERN NEGROES

BY HOWARD W. ODUM

WHEN THE BAND BEGINS TO PLAY:
Much has been said of the negro's love of music. It is needless to
repeat that a musical band in the community is enough to thoroughly
"demoralize" every negro within hearing distance.

The song "When the Band begins to Play" shows much of the complexity of feeling possible. Here, again, the negro is at his best in clownish portrayal of unusual scenes. His memory carries him back; his feeling idealizes the present. The chorus, always sung after each stanza, serves to unify the song; while the two-line refrain gives hilarity to the singing.

|: When de ban' begins to play, :| (three times as chorus)

See dat mule a-comin', ain't got half a load,
If you think he unruly mule, give him all de road,
Whoa, mule, whoa! Whoa dere, I say!
Keep yo' seat, Miss 'Liza Jane! Hold on to the sleigh!

Had ole banjo one time, strings made out o' twine;
All song I could sing was "Wish dat Gal was Mine!"
An' it's whoa, mule, whoa! Whoa dere, I say, etc.

Sung like the above, each of the following stanzas of two long lines,
but sung with emphasis and pause as if four short lines, is followed
by the two lines as refrain, "whoa, mule," etc., with the original chorus,
"When the band begins to play," following each stanza. This, too, is
the negro's vaudeville song:

If you want to see dat mule kick,
If you want to hear him hollar,
Tie a knot in his tail,
An' poke his head through a collar,
Den you kin hollow, "Whoa, mule," etc.

He taken her down to blacksmith shop,
To have her mouth cut smaller,
She made a whoop, she made a squall,
Den swallowed shop an' all.

Keep yo' seat, Miss Liza Jane!
Don't act jes' lak a fool.
Ain't got time to kiss you,
'Cause I'm tendin' to dis mule.

Ole master had little ole mule,
Name was Simon Slick,
Dey tied a knot in his tail,
Oh, how dat thing did kick!

An' it's whoa, mule, whoa! Whoa dere, I say!
Keep yo' seat, Miss Liza Jane! Hold on to the sleigh,
When de ban' begins to play.

Richie