Drawing on over one hundred interviews with industry insiders, former Spotify employees, and musicians, Mood Machine takes us to the inner workings of today's highly consolidated record business, showing what has changed as music has become increasingly playlisted, personalized, and autoplayed. Building on her years of wide-ranging reporting on streaming, music journalist Liz Pelly details the consequences of the Spotify model by examining both sides of what the company calls its two-sided marketplace: the listeners who pay with their dollars and data, and the musicians who provide the material powering it all. The music business is notoriously opaque, but here Pelly lifts the veil on major stories like streaming services filling popular playlists with low-cost stock music and the rise of new payola-like practices. For all of the inequities exacerbated by streaming, Pelly also finds hope in chronicling the artist-led fight for better models, pointing toward what must be done collectively to revalue music and create sustainable systems.