In a perfect world, all our songs would be easy to customize without extensive witchery, hacking, and DAT file swapping.
What tune would you like to have playing for each song? Classic music, pop music, no holds barred, as long as a single line of the melody could be ported over to a midi file. (Just assume SE ported in the FF Tactics synthesizer for flute and harp so it doesn't sound like a MIDI file.)
Marches: The Allegro first movement from Ralpha Vaughan Williams "English Folk Songs." Nice and upbeat.
Ballads: Vivaldi Four Seasons, Summer, second movement. It is really mysical sounding to me.
Paeons: Pictures at an Exhibition, first movement, Prominade
Mazurka: The benny hill music!
Prelude: Eye of the Tiger
Requiem: ... Dubstep. Any of it. You and I both know it causes physical pain to listen to.
Elegy: Saturn, The Planets, Gustav Holst
Dirge: Funeral March for a Doll, Tchaikovsky
Finale: The opening strains of Beethoven's 5th
Minuet: We are the Champions
Madrigal: We will rock you
Threnodies: ... I got nothing
Carols: Colors of the Wind (maybe that's too cheesy)
My only concern with some of these would be repeated playing gets just as annoying as the actual bard music, but at least it'd be a little more variety (even if only four of them would get played on a regular basis.)