Movie theater soundtracks - The most common use of Dolby Digital music is in the soundtracks of movies shown in movie theaters. The 5.1 or 7.1 channel surround sound is typically encoded in Dolby Digital format.
Streaming media - Streaming media services such as Netflix, Hulu, and Amazon Prime Video also often use Dolby Digital music for their audio output. This is especially common for streaming movies and TV shows.
Digital television broadcasts - Digital television broadcasts often use Dolby Digital music for the audio. This is typically the case for over-the-air digital TV broadcasts as well as satellite and cable TV broadcasts.
Gaming - Some video games also use Dolby Digital music for their audio. This is mostly common for games played on game consoles such as the PlayStation and Xbox.
It's worth noting that while Dolby Digital music is still prevalent in certain areas, newer and more advanced audio formats have emerged and are progressively gaining popularity, specifically, Dolby Atmos and DTS:X.