Can Animate Objects be used to make musical instruments produce that instrument's music?
The spell's description is a bit vague as to how much control you have over animated objects for non-combat purposes.
Wind instruments probably wouldn't work but I'd assume mechanical instruments could work, such as accordions or drums.
Animate objects (PHB, p. 213) says:
[...] Each target animates and becomes a creature under your control until the spell ends or until reduced to 0 hit points.
[...] you can mentally command any creature you made with this spell if the creature is within 500 feet of you (if you control multiple creatures, you can command any or all of them at the same time, issuing the same command to each one). You decide what action the creature will take and where it will move during its next turn, or you can issue a general command, such as to guard a particular chamber or corridor.
From the above, it seems clear to me that you can command all of the instruments to "play", which given that they are instruments, they should be able to do without issue. That said, if, say, you commanded them to play themselves, then their Charisma (Performance) apparently wouldn't be very good, because:
An animated object is a construct with AC, hit points, attacks, Strength, and Dexterity determined by its size. Its Constitution is 10 and its Intelligence and Wisdom are 3, and its Charisma is 1.
That said, as DM, I would simply allow them to be played competently because they are musical instruments, but other DMs may rule differently (perhaps if they ruled that the instruments lacked any creativity to perform well or something along those lines).
Generally speaking, though, from a more narrative perspective, there are only two reasons I can foresee where this would happen; either you're the DM and you want a cool scene where instruments play themselves, in which case of course it should work, or your are a player who wants to do something cool with one of your spells, in which case I would encourage any DM to allow it to work and create a cool moment.
So first of all, obviously the spell doesn’t say anything about music instruments. However, it does give us some information.
First of all, its mental abilities are really low:
its Intelligence and Wisdom are 3, and its Charisma is 1
Its questionable if the object would understand an order as complicated and vague as play music, and even then playing music is normally grouped under Performance which is primarily governed by Charisma, which these things are abysmal at. You could certainly order a violin bow to stroke a violin, or arguably even the violin strings to vibrate without external input, but the result likely won’t be what a discerning observer would describe as music.
Unfortunately senses other than sight usually aren’t talked about in monster statblocks, but the creature is listed as having blindsight and it only listens to commands you give it mentally, which might indicate that the creatures are supposed to be deaf which might further complicate any musical performance you might try to put on using them.
A drum is an object, a drumstick is an object. You could conceivably animate some drum sticks and order them to bash on a drum though. This is just a side note to remind you that you’d have to animate these bits separately.
Like I said, I think there’s a good argument to be made that Animate Object as written probably can’t be used that way, but it’s such a minor usage I also can’t think of a good reason why you wouldn’t let a spellcaster do this anyway.
The text of the spell is clear in that animate objects lets you:
...mentally command any creature you made with this spell if the creature is within 500 feet of you...You decide what action the creature will take and where it will move during its next turn, or you can issue a general command, such as to guard a particular chamber or corridor.
Now, exactly how this will work will be up to a discussion between you and your DM (or between you and your player), but there are some considerations that you'll need to cover and agree on:
Is the instrument capable of making a noise by itself? Can a woodwind or brass instrument draw air? Can a stringed instrument vibrate it's own strings and/or do you need to also animate a bow? Can a percussion move itself and/or do you need to animate a drumstick or something similar?
How well can the instrument play? There is no indication that animate objects provides proficiency in musical instruments. Just being an instrument doesn't necessarily give it the capability to play itself well. It can make noise, but how good of a noise? Looking at the stats, with an Intelligence of 1 and a Wisdom of 3, it is unlikely to understand itself well enough or even be good enough to play itself well. A DM could ask for a performance check or something similar for the instruments, but they may be less than satisfying for a listener.
