On the surface, yes, that is a perfectly fine thing to do. However, I think more information is needed to determine if it's actually a good idea. If it was just a casual hobby and you played guitar for, say, a few hours each week, it might not sound that impactful to write about how meaningful it was to you to tinker with it here and there. If, however, you have put quite a lot of time into it over those 8 years, then it will probably be something that you can write well about. If you've put a ton of time into it, your writing about its meaning in your life will sound a lot more sincere than some random fluff you made up about 50 hours of clinical volunteering that you only wrote about because you thought it would sound better to talk about clinical experiences.