Moon June spoon

Shorthand for the old-fashioned Tin Pan Alley pre-rock and roll lovesong. It comes, I think, from the rhymes in "By the Light of the Silvery Moon", but I'll bet there were many other offenders. Robert Wyatt, on Soft Machine's "Moon in June", lampooned, with playful sobriety, this sort of sentimentality, a thread picked up later in Gang of Four's "Anthrax". These hipper-than-f*ck modern days have merely swapped new rhymes, clichés, and morals for old. Same crap, new wrapper.

Or, "moon June swoon."

A disparaging adjective used to describe work by poets and lyricists who lack the creative energy or ability to move beyond the most obvious and simple rhymes.

Example:

He possesses a bent for sheer melodicism, and the kind of quick, lyrical gift that make the "moon-June-swoon" school of songwriters look like teeny-tiny babies.
(Source: www.metroactive.com review of Billy Bragg's album William Bloke)

The expression is derived from the relative ease with which one could create a simple love song using easily rhymed "-oon" words, of which there are several that fit tired romantic cliches.