While its not a "side hustle", Ive been making electronic dance music for 25 years, and making music, especially pop songs, the design thinking process definitely comes in

You make a demo (prototype)

You test it (show it to friends or other musicians)

You get feedback

You go back and tweak your demo

I know many people have a song they have in mind that they were influenced by or want to compare it to, its called a reference track, so you definitely do competitive analysis , see what other tracks that are somewhat similar to yours and what they sound like, especially if you are trying out a very specific genre like Jamaican dub music