Hello @danainspan !
This is Lana from Shopify.
When it comes to themes, it is possible to customize any of the themes to suit any type of business, even if they weren’t created with a specific type of product in mind.
You mentioned that you were originally using the ‘Kala’ theme and found that it was not compatible - it is not a theme from our own Shopify Theme Store so I cannot suggest support options for it, but I would recommend you look into it with the developers of that theme if possible. They might be able to help you out if you let them know what features are missing or why you found it to be incompatible.
If you are settled on choosing a brand new theme, I did take a look at our Theme Store, and here you can see several options I found under the search designed for musicians - they may not be using that type of store as a placeholder in the examples, but they have features and layouts similar to that of other stores catering to musicians. The examples even include some of our free Shopify themes, which are Debut and Narrative.
The advantage of using one of our free themes over a paid theme is that it will be fully supported by us, so we can look into it if something breaks or even help make some coding changes using your Design Time. Do note that not all coding changes are supported, but you can look into this with our support and we will be able to guide you anyway, or you could even look to have features custom designed with Shopify Experts. Experts are freelancers that charge their rates based on the work that they do, they are trusted in the community and can work on any theme, regardless of whether it is one of our own or a third party paid theme.
For working on your own, we have guides in our Shopify Help Centre on Theme Customization where you can learn all about the possible ways in which you can alter your theme to suit your specific needs. You can even find specific guides for our free themes, such as this help doc on the Debut theme customization.
If none of the above options suit, please do tell me a little bit more about what specific features you’re looking for a theme to have, and I would be happy to help you look for one based on that.
Lastly, since you mention the sale of musical instruments, I thought you might like to take a look at one of our success stories from Shoreline Music - they have some useful tips and information for other stores in this industry.
Let me know if you have any questions here!
Thanks. -Lana