We are accustomed to thinking about pop music in terms of its most familiar metadata: songs and albums, scenes and artists. But what about all the other, seemingly incidental music that gets lodged in our heads, from commercial jingles to sitcom soundtracks? In the book “Koji Kondo’s Super Mario Bros. Soundtrack,” the theorist and composer Andrew Schartmann passionately argues for the radical legacy of video-game music. Focussing on Kondo’s much-loved score for Super Mario Bros.—and offering a brief detour through his Deep Purplish soundtrack for The Legend of Zelda—Schartmann brings readers into a world of visionary musicians producing beloved masterpieces in almost total obscurity. Could it be that the largely unknown Kondo, Nintendo’s first dedicated sound designer, was one of the great innovative forces of our time?