Assuming I know what I'm talking about:

>Okay. Echoes is a great song. But according to the helpfile
>it favors Comedic and disfavors Epic. Tragic and Romantic
>should be approximately equal.

This is all consistent with the way I think it works.

>While we're on this topic, though, a question for Nep.
>Regarding instruments, does a bard want to match his
>instrument to the repertoire he's using or to the preferred
>repertoire of the song he's singing (assuming it's different
>from his current repertoire)?

Match to your current repertoire.

>For example, suppose you're a tragic bard using tragic
>repertoire and you're going to sing symphonic echos, which
>favors comedic and disfavors epic.
>
>You have one instrument that's "very good" in tragic but "very
>bad" in comedic. You have another instrument that's the
>opposite: "very good" in comedic but "very bad" in tragic.
>Which one would give the best results?

The instrument that's good for tragic.