Tony Shalhoub’s long-running police procedural Monk switched theme songs after the first season, but the show never explained why. Thanks to all the great episodes of Monk, Shalhoub’s police procedural became one of the most beloved TV shows ever. There are so many iconic elements at play that helped it gain a huge following, from Adrian’s idiosyncrasies to all the famous guest stars Monk was able to secure. One of the most memorable parts of Monk – its theme song – actually changed partway through the show, and the series never explained why.

https://screenrant.com/monk-season-1-theme-song-changed-why-explainer/