I'm not sure that doing an fMRI while playing cello will tell you anything important.
I read a book called How Emotions Are Made by Lisa Feldman Barrett
https://lisafeldmanbarrett.com/books/how-emotions-are-made/
The short version is that basically there is no "fingerprint" of emotions that can show up in brain scans or other biomarkers. The brain adapts and can generate similar feelings from different parts of the brain. This is called "degeneracy" in biology.