Diatonic harmonicas: these are the standard 10 hole harmonicas. Each is tuned to a specific key, this is why harmonica players have multiple instruments (more on this here). When I started, everyone used the Hohner Marine band harmonica. Some still do.
New harmonica models have since appeared, there is more choice. Moreover, harmonica customisers now prepare high end versions of the diatonic harmonica, based on the pioneering work of Joe Filisko. Neil Graham is a student of Joe’s customisation method, and one of only three approved Hohner harmonica customisers. Fortunately for me, Neil is based in Australia. I have 12 of his instruments.
Half of these custom diatonics are tuned to Major Cross, a tuning system I devised for bluegrass and Irish fiddle tunes. Seydel have released a Major Cross harmonica, shown opposite. We worked together on this, needless to say I am very happy with the result. Thanks Seydel!
In recent years I’ve taken to the tremolo, and like it very much. It sounds like an accordion, to me at least. I’ve created a set of online tremolo harmonica lessons, they are here. More details are at TremoloHarmonica.com.