Opening theme

The opening theme song of the popular TV show "How I Met Your Mother" is performed in the original key of B-flat major. The music was composed by the acclaimed American composer and lyricist Carter Bays, who also co-created the series. The song is performed by the show's cast member, a Canadian musician, and actor named Jason Segel. It is interesting to note that the lyrics of the song were altered slightly in each season to reflect the evolving storyline. Additionally, the melody of the opening theme is catchy and upbeat, featuring a combination of acoustic and electric guitar, giving it a distinctive and memorable sound.