Study music is any music people put on while reading, revising or working, chosen less for close listening than for a steady, pleasant atmosphere. Jazz lo-fi has become one of its best-known forms: mellow tempos, soft Rhodes chords, muted drums and, above all, few or no vocals.
Research supports some of these choices but not grand promises. In a randomised study of young adults, background songs with lyrics hurt performance on attention tests more than music without lyrics, which fits the wider finding that words compete with verbal tasks. Other experiments suggest that any short-term boost from music comes largely from better mood and alertness rather than from the music itself. Effects vary with the person, the task and the volume, and for the hardest problems silence can still work best.
A sensible approach is to keep the level low, favour instrumentals and notice honestly whether a given playlist helps or distracts.