Unless something is mis-labled, if a spell prep covers "ALL" circles, then it applies to every spell our character casts without any circle limitations. (So, yeah, it'd apply to both the bard and minor elemental circles.) If you get one that is for "all" and then another one that is for just the "minor elemental" circle (and appropriately order it in your PREP PHRASE list so the minor elemental prep is higher priority than the all prep), then your bard will use the minor elemental-only phrase when casting a minor elemental spell, but any other spell (in this case a bardsong!) would use the "all" phrase. And then if you were to get a custom spell prep for just ONE song (and, again, have it higher priority in your PREP PHRASE list than the circle-wide or all-spell phrases), you'd use that super fancy spell-only one for casting just that spell, the minor elemental one for casting for other spells in that circle, and the all one for casting any other (bard) spell. Hopefully that clarifies!

- Overlord EK, who has some prep phrase experience

>You now regard Eorgina with a warm demeanor.