I think you are misunderstanding the definition of "principle place of business." See IRS publication 587 page 3-4 and IRS publication 463 chapter 4.
https://www.irs.gov/pub/irs-pdf/p463.pdf
https://www.irs.gov/pub/irs-pdf/p587.pdf
Particularly example 1 on page 4 of publication 587.
Your home office will qualify as your principal place of
business if you meet the following requirements.
- You use it exclusively and regularly for administrative
or management activities of your trade or business.
- You have no other fixed location where you conduct
substantial administrative or management activities of
your trade or business.
Your home may be your principle place of business if that is where you do the management and administrative activities -- scheduling gigs, doing your bookkeeping, issuing invoices, etc. Rehearsing and storing equipment adds to the business nature of the home. It it not necessary to take the home office deduction to show that your home is your principle place of business, but if your home is your principle place of business, you may indeed qualify for the home office deduction as well.
If your home is your principle place of business, then all your mileage to other work locations is a business expense.
If your home really is not your principle place of business, then you can only deduct mileage when you drive to a second or third job site in the same day. Your first trip out from home to site 1 and your last trip back from site x to home are non-deductible commuting.
And as always, for any mileage deduction, you must have accurate records that should include at a minimum, the date of the trip, business purpose, and miles driven. There are log books and diaries made for this purpose that you keep in your car, and there are probably smart phone apps these days too.
