Working with a Low “4th A4 Number” Piano

Pianos with low 4th A4 Numbers don’t really – or shall I say – haven’t yet, caused me much problem.

I’ve come across pianos whose ‘4th A4 Number’ is 0.0 c.!   I didn’t know that was even possible until I measured one.   Yes, what that means is that when the A3/A4 octave is tuned as a pure 4:2, the A3/A4 2:1 is also pure.

Some technicians believe that this is a sign of a well scaled piano.   I’m not so sure about that.  My first one was a Yamaha Studio Console.   It’s a nice piano, but I’ve never found a 0.0 4th A4 number on a long scale Steinway,  Yamaha, or Kawai.

The first time I found one, I must have checked all my tuning and measuring 3 or 4 times to make sure I wasn’t missing something.   But each check confirmed the last.   On this piano, a pure A3/A4 4:2 resulted in a pure A3/A4 2:1.

These pianos don’t require nearly as much work as the high 4th A4 number pianos.   I think the danger with these really low 4th A4 Number pianos is tuning the prime octave too wide.   I’ve also found that a prime 5th @ -1.5 c. is too wide for them.

I’ve found relatively low 4th A4 numbers on some Kawai RX 2’s and 3’s.   I was never really happy with a RX2s in one of my churches until I let the 5ths be a little more narrow than my go to -1.5 c.  setting.   The prime 5ths ended up being closer to -1.8 c. or so.   At that slightly narrower setting the tuning really came together.

When the 5ths were tuned @ -1.5, I thought the octave sounded a little too noisy.   It wasn’t near the 2.8 c. wide prime octave 2:1 mark either, so I’m not sure what it was that bothered me about the way the prime octave sounded.  But a little less stretch in the prime octave made it sound better.

I then based the widths of the 5ths off of the prime octave, and they (the 5ths) ended up being a little narrower than -1.5 c.

And the octave sounded better. I think on some of these low 4th A4 Number pianos, the prime octave just shouldn’t be stretched very much at all, which is what resulted in the slightly narrower prime 5ths.

After tuning this RX2, and leaving the prime octave a little less stretched (still wide but not by much) and with a pair of more narrow prime 5ths – somewhere around -1.7 or -1.8 – I was happier with the tuning than I have ever been before.

Another reason why I think leaving the prime 5ths a little more narrow on those pianos, is how our spreadsheet handled creating the tuning given my mapping settings.   In the past there was always this ‘S’ shape in the curve in the tenor.   But after mapping it leaving the prime octave a little less stretched and the prime 5ths a little more narrow, that ‘S’ shape in the tenor range was gone.

Those RX2s are nice pianos, and I think I may have finally learned how to tune them.  And in the meantime have learned how to deal with other low 4th A4 Number pianos.

I find it interesting how it seems like working on a piano with a low 4th A4 Number results in a slightly more narrow prime 5th, just like it does working with a high 4th A4 number:  both results in slightly more narrow prime 5ths.