If I recall correctly, Bart sang the "I'm a Little Teapot" song for them for a dollar. One line in the tune goes "I'm a little teapot, short and stout; this is my handle, this is my spout."
In order for Bart to have sung a "spout medley," he would've had to include a few other tunes that mention spouts. I don't remember whether or not he did, but in any case "spout medley" is a one-off joke, not a common reference.
For example, I could jokingly announce "I am pleased to present my Aquatic Medley" and then sing pieces of "Blue Bayou," "Down by the Lazy River," and "Fire Lake."