As a fairly new bard I have been asking about both defensive and offense ways to use this seemingly Gamebreaking Cantrip here is what (with some lucky rolls) I have gotten away with so far (or tried to)
-Summon Gong: I and my team set off an arrow trap in a 5' wide hallway, and lightning fast i yelled "Summon Gong" (rolled 18+mod) and got a gong (the diameter of my characters wingspan) made of bronze that blocked the attack entirely.
**note I have rolled too low on that trick and gotten finger cymbals... and an axe to the shoulder**
-Summon Great Bell: Classic cartoon move, my NPC dwarven sidekick and I have a move in which I summon bell on the head of the NPC within melee range of me, based on roll, it is now blind and if my dwarf lands a mace strike on the bell, they are shaken. Again, all depends on rolls.
-Summon Susaphone: bit of a crapshoot, but sometimes in a panic i summon this as a standard action and lob it towards the attacker. Skeletons/Zombies seems to always try to catch it and sometimes drop their weapons... not my favorite, but has been effective.
and last and probably impossible to pull off
-Summon X/Sonic Burst:
you cant really direct the instrument you summon, it poofs into existence in front of you and you grab it, BUT if you were to use say, Sonic wave/burst what have you as your second action you could (depending on the level of wtf your DM puts up with/rolls) propel said instrument fwd dealing physical dmg along with the d8 of sonic.
Worth a shot right? Am I crazy?