Harp Keys (how can I tell)

How can I tell what key a harp is in?

this is the sound I’m looking for

I usually listen for what note the song resolves to. Alternatively, if you know what key the song is in, you can start with that Key and count up to the 4th of that major scale to determine what harmonica you should use.

As an example, if the song is in F, The F Major scale is: F | G | A | Bb | C | D | E | F. The fourth note is Bb, so that’s the harp you’d choose if you were playing cross harp (2nd position).