Hohner has released a new altered tuning diatonic harp called PentaHarp.
In Pat Missin's Altered States list of altered tunings, this tuning is 11.15, "Blues Scale Tuning" which has been known since the 90s.
PentaHarp offers you draw bends from bottom to top. The same breath pattern is repeated and there are no blow bends.
You can order pre-tuned PentaHarps but it's possible to convert a Standard Richter harmonica. The conversion to PentaHarp is a pretty big job. The blow and draw reeds in four holes need to be swapped to avoid having to sharpen notes. It's much more effective to lower the pitch or reeds instead of raising them. The job is much easier and the reed playability will stay protected.
PentaHarp adds three semitones to the total range of the instrument compared to Standard Richter. We will add these extra semitones on the bottom end of the instrument, not the top.
So we will start with a harp that is three semitones sharper than the key we are aiming for and tune it down.
Here is a visual aid to the modification:
1- Swap blow/draw reeds 7, 8, 9 and 10. This will really make things easier.
2- Perform coarse tuning adjustment. Lower pitch using BluTak or Solder.
3- Perform other customizing and improvements
4- Perform fine tuning. No major chords are present but there are lots of opportunities for harmony in splits and octaves. Tune all minor thirds to zero. Tune Fourths and Fifths to be in harmony with the tonic (Fourths are about -2 cents and Fifths are about+2 cents)