Well, that could work. Note however, the target creature must be hit in a cloud, not burst, of syndrome substance, and that it's impossible to start fires, unfortunately, with that method (note that the other method cannot start a fire too.)
Anyway, you should try to keep the riffing diverse and effective, a slow spell is obviously outclassed if there are no expendable reagents, and collecting those reagents require a bag, removing the reagents one by one, and putting and using them with your hand.
You could try to make tiered guitars for better spells, or replace the tiered guitars with tiered picks.
I think I'll utilize different picks for different riffs. From my experience with this, an item with a boiling point of 0 will not explode the moment it is made allowing you time to throw it and have it burst into a cloud near or on the target. While one can't start an actual fire, they can still cause burns this way with an incredibly hot material bursting into a searing cloud. If the ignite point is low enough, you might be able to make the cloud flaming but I haven't tested it yet.
Removing items from a container and making items happen in hammertime, so there isn't much to worry about there (or it looks like they do anyways. My flute-playing human was able to remove several ingredients and create an explosive melody before the honey badger even moved)
I'll probably start by making a single basic "pick" tool. This tool can be modified using some other ingredients to create decorated picks (A celtic knot pick for the folk/folk metal magic, for example). I'll have a simple set of basic chords that can be created without a pick, the in-game logic is that you're finger-picking. I don't think I'll require you to have any special ingredient to play a song; once you have a pick you can play any riffs or chords it allows. The difficulty would be in acquiring the necessary materials to upgrade your pick.
I'm also considering allowing the material of the pick to come into play as well, but I'm not sure in what way and it might clutter the creation screen too greatly.
The next issue is just deciding what sort of chords and riffs each type of pick will be able to make. This will be a lot easier when the syndrome updates come in, so for now I might just make a skeleton crew of spells with each pick only really unlocking a single new spell. The death metal pick allows for a brutal riff causing necrosis, for example.
Does anyone know if the quality of an item at all matters when you're throwing it? If it does, I'll tie the creation of picks, guitars, and songs all to the same skill and make the riffs a toy so that quality matters. If not, I'll not bother with that and instead just have the riffs be a glob of a material called "Brutal riff" or "Basic chord" whatever.