I have a Harp in C but I would like to know what key this song is played in and how I can find the instructions on how to play it just like in the album
Funny thing about this song. It’s played in D, but the guitar is tuned down a half-step, which puts the song in C# (Db). So, if you’re playing along with the recording you’ll need an F# (Gb) harp. If you’re playing with a guitarist, I doubt one would want to tune the guitar down, so for that you’ll need a G harp. I can’t tell you where to find instruction on how to play the song, but with the right harp maybe finding the notes by ear will be easy enough.
More stuff you didn’t ask for: Generally for rock and blues, the harp in the key of the forth interval of the key of the song is used. For example, if the tune is in G a C harp is used. If the tune is in E an A harp is used. The interesting thing about Don’t Follow is that the song is not based on the blues genre, and some players would have chosen to use a harp in the same key as the song. Choosing the harp in the key of the forth gives it a slightly dissonant twist because of the contrast between the pop chords/melody and the blues scale on the harp.