This is an entirely different discussion, probably best tackled on a separate thread. I remember the Basschat Collective coming to the conclusion that, if you are a weekend warrior, you usually end up spending more than you earn, if you take into account buying equipment, maintenance, paying for travel etc. (which you have to do). So HMRC may allow you to self-assess your earnings and your expenses for a while, then it tells you you should consider your activity a hobby and stop wasting their time.
If you are a pro, that's a totally different matter.
Having been freelance all my life (not as a musician), I object to being thought as dishonest by default. Remember that the reason why we can detract all kinds of expenses from our income, so we end up paying less tax, is also to compensate for the lack of sick and holiday pay and lots of other benefits that employees have and we don't.