I agree, that from a structural perspective you shouldn't include other brands, but also from a Click Through Rate (CTR) perspective, when someone is searching for a brand they are likely to be searching for a major, already trusted site. You need to make sure you can differentiate this change from your other non-branded keywords. Negative keywords are your friend!
Make sure your ad copy is strong.
Here's how I would suggest you structure this at the campaign level
Guitars
Drums
Guitar Brands
Drum Brands
Brand (your brand)
Competitors (if you have the money, don't start here)
Be sure you have a clear Call to Action in your ad, and at least 1 keyword in the Headline. Also, send specific traffic to the most useful page on your site. DO NOT send this traffic to your home page. That won't be useful for your spend.