Dear Dan: I'm sorry that in my thinking I was restricting my comments to the Temper- ament section. You are right. Most of my tuning these days involves the use of the FAC stretch on the Sanderson AccuTuner. My current experimentation involves altering the stretch numbers in order to make the 5ths in the temperament section less narrow by giving as much as .4 cents addition to the stretch number of A4 and then stretching the C6 stretch number as much as 2 cents which in turn will make the C8 about 10 cents sharper than without this change. When one does this, there are some tricky consequences to consider at the locations where the partial changes come. This can be handled very well by doing some careful resetting of the pitch level of the machine. I will write an article about this later when my results are more definite and consistent. You are indeed sharp to recognize this problem. Sometimes this problem occurs only because of less care in selecting the correct stretch number in the first place. However, we still have the problem of not knowing where the wire size changes occur (at least the machine doesn't know where they occur). In case you may be interested, I am now working toward providing much sharper high treble tuning which I now think makes a piano sound better. A tip on how sharp to make the treble involves keeping the octave-5th pure up to about C7 and then balancing the stretch of the double octave so that the octave-5th becomes sharp or on the wide side until the double octave-5th is equal beating on the narrow side. This makes the triple octaves sound better at the expense of the single octaves, but the overall sound of the piano is better, at least in my opinion. You may have fun experimenting with this.
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