Building a music app involves several steps, starting with defining core features like user registration, music streaming, personalized playlists, offline downloads, social sharing, and integrations with music databases. The app should support various platforms (iOS, Android, Web) and include robust backend infrastructure for data management. For revenue, consider freemium models with ads, premium subscriptions, and partnerships. Your business model should focus on user engagement, offering personalized content, and creating partnerships with artists and music labels to expand your library and user base.