If you update to Big Sur from Mojave or earlier, the iTunes application will not function and cannot be launched.
Inside the bundle was a perfect replica of the iTunes 9 interface—the last “great” version, before Apple killed the visualizer and the integrated store. It was running as a live process, hidden from Activity Monitor. And in the “Now Playing” slot? itunes macos big sur 117
: This is a popular open-source third-party tool that allows you to run native iTunes on modern macOS versions. However, it can require disabling some system security features and may suffer from stability issues on newer updates. If you update to Big Sur from Mojave