Recently on pianoworld.com, there has been some discussion concerning different types of unisons. Some claim to be able to tune unisons within 0.1 of a cent consistently. Some claim to be able to tune each unison to a different tolerance and create unisons with varying tone qualities.
What I have done on this page is post recordings of a single A4 unison that I tuned 10 different ways, each unison is tuned to under 0.9 cents difference and would therefore score 100% on the PTG RPT exam.
The cents offset was measured using Tunelab97. Two or three measurements were taken of each separate string, and averaged. If one measurement was drastically different from the other two, it was omitted. For example, sometimes a string’s attack would be very sharp but the pitch would immediately settle down and record identical middle and ending offsets.
The measurements were taken at the attack, at about 1s if needed, and at 2s.
These are the conclusions that were drawn:
1. There definitely are different styles of unisons possible within the PTG’s criteria of an acceptable unison.
2. The five types of unisons that I was able to produce were:
a. Partial Swelling Unison. One partial tended to swell and in one case, unison #8, the beating was so bad at the 3rd partial that it would have been identified by examiners to be marked, but would have passed with an offset of 0.41 cents. In this case, a skilled technician would have tuned the unison so that the beating of the 3rd partial would have been less, but maybe the 1st and 2nd partial would be rolling a bit more, yet the tone of the unison as a whole would have been better. Unisons 1, 2, 3, and 8 exhibited individual swelling partials.
b. Cascading Unison. The partials swell in a cascading fashion, usually a higher partial swelling and then the one below it swells, and so on, creating a sort of wave of swelling partials from top to bottom. Unisons 4, 9, and 10.
c. Swelling Unison. The general tone of unison increases in volume, usually on the 1st partial. Unison 6.
d. Sustaining Unison. The volume of some or all of the partials seems to hang and not diminish as fast as the others. Unisons 5 and 10.
e. Toneless Unison. The partials seem to die away quickly leaving no sustain or tone to speak of. Unison 7.
There were unisons that exhibited a combination of different unison characteristics. Unison 10 was classified as a Cascading Sustain. Its partials waved in a cascading style but then grew in intensity. It had a very rich and colourful tone.
The recordings of the unisons are shown below with the visual demonstrations of the partial intensities, thanks to the Soundbeam program.
These unisons were all made using the same two strings of A4 from the same piano, all tuned and measured within one hour. The variety of tone produced was fascinating. I hope you enjoy listening.
UNISON 1:
Offset: 0.12 cents
Quality: Partial Swelling
Notes: The 2nd partial decreased in intensity rather quickly.
UNISON 2:
Offset: 0.06 cents
Quality: Partial Swelling
Notes: Swelling of the 1st partial.
UNISON 3:
Offset: 0.79 cents
Quality: Partial Swelling
Notes: Swelling of the 2nd partial.
UNISON 4:
Offset: 0.76 cents
Quality: Cascading Unison. A nice swelling of the 1st partial.
UNISON 5:
Offset: 0.49 cents
Quality: Sustaining Unison. 1st and 2nd partial sustain nicely. The 1st partial swells at the end.
UNISON 6:
Offset: 0.15 cents
Quality: Swelling
Notes: The 1st and 2nd partials increased in intensity at the end.
UNISON 7:
Offset: 0.10 cents
Quality: Toneless
Notes: The partials died out quickly and there was less tone in the unison. This is the type of unison that I would work on to get some more tone out of it.
UNISON 8:
Offset: 0.41 cents
Quality: Partial Swelling
Notes: The 3rd partial was beating excessively.
UNISON 9:
Offset: 0.25 cents
Quality: Cascading
UNISON 10:
Offset: 0.47 cents
Quality: Cascading Sustain
Notes: The nicest tone in my humble opinion. The 1st partial sustains at a high volume.
