This text comes from Songs of the Cowboys, a historical songbook transcribed on Wikisource and reproduced from the pinned revision linked below.
His mammy’s a burro, his daddy’s a horse;
Of course you’ll all think it’s a mighty queer cross.
He’s got brains in his eyes, he’s nary a fool;
As smart as a cricket, my little brown mule.
He’s always in mischief, he’ll shy at a bug;
When he sees a tin Lizzy he’ll jump like a frog;
He’s a voice like a trumpet, his coat’s always bright;
He’s as gentle as can be if the cinch is n’t tight.
Just pull on that flank cinch a little too long
And he won’t do a thing till you are mounted and on;
Then farewell, relations, good-bye to the crowd,
For you are off on a journey high up in the clouds.
At night I don’t stake him, just turn him foot-loose,
And inside of two hours he’s as full as a goose;
He’s a great old camp-robber when the boys are in bed —
Roots among the bake ovens for bacon and bread.
He’s a great one to wrangle on, he knows every horse,
And if one of ’em’s missing he’s as mad as the boss;
His sense just come natural, he was never in school,
He’s as wise as a parson, my little brown mule.
Did you ask if I’d sell him — well, not on your life;
The day we were married I gave him to the wife;
And now two of my kids daily ride him to school;
Oh, no, money can’t buy him, my little brown mule.