D is for Dorian, and "don't mistake it for minor mode."
Not only is this song a good idea to play in class, mostly due to its complete lack of offensive material, but playing an arrangement for a young jazz band also leads to a great deal of discussion of Dorian mode in jazz tunes. While in some cultural circles, Pharrell's biggest hit is considered a false flag in tough times, you have to also consider that it was originally penned for a kids' movie (Despicable Me 2, for which Williams also wrote the score). You have to also consider the absolutely impeccable and yet not overwrought production on the track.
Intro: Already a Grammy winning producer and successful film composer, Pharrell Williams dominated popular music with “Happy” in 2014. Nominated for an Oscar having been featured in the movie Despicable Me 2 (it lost to the Disney juggernaut "Let It Go"), the song then reached #1 on the Billboard charts, remaining there for 10 weeks. It hit #1 in 27 different countries besides the US and has sold several million digital copies worldwide. It was Billboard's #1 song of 2014 and the following year the song won Pharrell Williams Grammys for both Best Pop Solo Performance and Best Music Video.
Analysis: Although described in some outlets as being written in a minor key, the song was actually written and is performed in F Dorian mode, as the song continually returns to a home pitch of F, despite working in the same key signature as Eb major. Many printed versions of the song indicate the key as F minor (relative to Ab major, but with most of the D flats made natural) or in Bb major, but with most of the As made flat. Thus, F Dorian seems to be the most arguable key. The song is not entirely pentatonic, but it makes use of a pentatonic scale (Eb – F – Ab – Bb – C) in its melody.
Considerations for Teaching: A highly current and familiar song, this is an excellent example to play for students when disseminating the harmonic difference between Dorian mode and minor key. This song contains no offensive language or subject matter.