Harmonicas are a great addition to any musician’s inventory. From the solo on Billy Joel’s “Piano Man”, to the introduction to Neil Young’s “Heart of Gold”, it’s clear the Harmonica works with almost any instrument.
The most common incarnation of the Harmonica is probably the Diatonic or “Blues Harmonica”. This is the instrument played by many folk/rock artists like Bob Dylan. They can be a fantastic addition to the repertoire of any musician, allowing for a greater catalogue of songs.
Diatonic harmonicas are set into a fixed key (e.g. G, E or C) and the song will need playing in this key if they’re to sound at all in tune. However, you can often transpose the guitar or accompanying instrument.
You might also like to look at a Chromatic Harmonica. Although less common they offer the flexibility of having the full range of notes at the push of a button. Push the button and the available notes goup into their respective sharps: C – C#, E – F, etc. Perhaps the best known user of a Chromatic Harmonica is Stevie Wonder.
While versatile the Chromatic Harmonicas do have limitations. A degree of musical theory knowledge is required to get the best out of them. On top of this being single reed means that bending a note will not sound as good as the Diatonic Harmonicas. These limitations mean they are more popular in Jazz and Classical Music as the range of notes is greater despite the lack of expressive features.