tuning Hohner 64 chromatic

If by concert pitch you mean the standard pitch that uses A440 (A above middle C vibrating 440 times per second) as a reference, then most harmonicas are tuned higher than this. This happens for at least two reasons:

• Breath pressure during playing depresses pitch, making the reed vibrate slower than its tuned pitch, especially on the longer, low-pitched reeds. 

• Actual concert pitch is often higher than A440. In Germany, the real-world standard pitch is A444, while symphony orchestras in the US often tune close to A446. Higher pitch creates brighter sound, and brighter cuts through and commands attention.

I tune my harps to A442. When I play with amateur fiddlers who tune to A440, I have to push pitch down to match them. When I play with orchestral violinists, they have to come down to match me.

Some individual players depress pitch so much that they have their harmonicas tuned high to compensate. For instance, Stevie Wonder has his chromatics tuned to A446 so that he won't come out sounding flat.

So, if you want to tune your own chromatics, a few things to consider:

• Tune to equal temperament so that you can play in any key. Tuning to Just intonation or to a compromise temperament works for diatonics, but is likely to produce unhappy results on chromatic unless you really know that you're going for specific results and will use your chromatic exclusively for those results.

• Tune to your own playing habits. If you don't depress pitch much or at all, maybe you should tune to a A442 or 441 or even 440. (but I recommend tuning a little sharp to give yourself some wiggle room). If you play really heavy, you may need to tune higher,. Check your playing against a tuner to get an idea where you should aim your results. 

• To avoid damaging windsaver valves, you can isolate the reed you're tuning simply by slipping a piece of paper under the reed you're working on and over everything else. Just be careful when doing this.