[the REAL Minos Prime]

I, for one, have never seen a spell that dealt sound damage, meaning that Screaming Tome is only ever adding half of its Power. Not just that, but it has a stat that not many people take for its scaling. I feel letting Screamer Tome be an instrument would not just balance out the fact it doesn't have spells that match its element, but also give Bard/Mage or Bard/Curate hybrids an option for spellcasting. 

Also, since it has an unblockable Silence cure (even if rather costly), it'd synergize with bards rather well, as if memory serves not even Herons can use bard songs while silenced.