When I have to study something really difficult I love instrumental music, especially in the classical style.
I pick the style of the music to match the type of material I am studying. If I am writing creatively, or persuasively I would listen to something of monumental sweep- here I have included Mozart’s Requiem. If I am doing something methodical, mathematics-based, programming, or logical (like writing an argument), then I listen to music that stimulates the mathematical sections of my brain- Bach. The cello suites and violin concertos can’t be beat. The Goldberg variations as played by Glenn Gould are some of my favorites.
To finish up the time I have included a delicious movement that has rich harmonies in minor keys that move forward with a hopeful and irresistible march, Beethoven’s Second movement of the 7th Symphony is a great and triumphal way to finish your study time.
I hope your studies go well!