"Minne +2" harp adds 10 defense to each Minne that you play. So if you do Minne 4 & Minne 5 at the same time, that is 20 extra defense compared to a BRD who doesnt use the appropriate instrument.
Soul Voice happens to double instrument bonuses, so with SV up & playing Minne 4 & Minne 5, you are now talking about 40 extra defense compared to a bard who doesn't use Harp +1
Oh and of course, using the right instrument adds 20 seconds to the song (doubled to 40 with troubador).
