Jim's Harp-O-Matic

This is a great reference for the tuning and tonal center of different tuning systems on the diatonic harmonica. Richter by the way is standard tuning. Try, "C" "Richter" "G" "Blues" and it shows a "C Major Diatonic Harmonica," "Richter" as the tuning system, "G" as the key you want to play in (2nd Position) with the root notes of the key highlighted (home base for soloing) and "Blues" as the scale and the scale is listed at the bottom of the page. Try the key of "D" under the "Melody" header and now you're playing in 3rd Position, highlighting "D" as the home base. Very cool.

Page: http://www.truechromatic.com/harp-o-matic.html

If you want a listing of all of the standard-tuned diatonic harmonicas, visit...

Understanding Position Playing
http://www.bluesharmonica.com/lessons/understanding_position_playing

...and download the PDF titled "Harmonica Chart [All Keys].pdf"