If I made a large purchase for my occupation, such as a musical instrument for myself, a military musician, can I claim this on my taxes?

[DMarkM1]

No.  The Tax Cuts and Jobs Act that went into effect for tax year 2018 through 2025 eliminated "miscellaneous itemized tax deductions" which is where items purchased for your occupation would have been listed.  

[mesquitebean]

While you may no longer be able to deduct anything as an employee job expense,  I know some musician employees (civilian) who also have some part-time self-employed work, such as side-gig performances, teaching private lessons to students, and other work as an independent contractor.    So if you have any self-employment income (1099-MISC, cash, etc.) in your music work as an independent contractor and thus file Schedule C, you may be able to allocate a portion of your instrument's cost to your self-employed work by depreciating a portion of it.   Allocating and depreciating can get kinda involved, and I'm not a tax expert, just a fellow user, so I can't help you further with that.   I'm merely mentioning it in case you do have any self-employed income from your music work.

ADDENDUM 1/23/20, 8:00 PM Pacific

I found some more info for you.  See my next comment below.

[mesquitebean]

@gamewarden96 

In addition to the above, I found some more information for you.  

Are you an armed forces reservist by any chance?

The following TurboTax FAQ lists a few instances where employee job expenses might still be itemizable (for those who can itemize) and mentions "Armed Forces reservist." 

It says there are also a few states that may allow employee expenses on the state return even if not allowed on the Federal return.  So it suggests entering the expenses, and TurboTax will tell you if they can ultimately be used or not.

See this FAQ:
https://ttlc.intuit.com/community/credits-and-deductions/help/can-employees-deduct-any-job-related-e...

Even if you met one of the qualifications or your state allows it, the question would remain about how to allocate and depreciate your instrument, or if some of it can be expensed, however.  Again, I'm no tax expert, just a fellow user.

Do you have access to tax services on your military base?   Many have an office to assist service people with tax issues.