Making sense out of cents

[Morgan28]

The app labels any frequency near A4 as "A" regardless of actual pitch. At 498.5 Hz:
- It's physically B4 (493.88 Hz), not A4 (440 Hz).
- The app only shows cents relative to your selected reference pitch (A=440, 445, etc.), not the true note name.

Why you see "A4"
The app forces nearby frequencies into A4’s "slot" and shows deviation in cents. Your reed is ~17 cents sharp of B4 (B4=493.88 Hz → 498.5 Hz is +17¢). But with A=440 selected, it mislabels 498.5 Hz as "A4 +16¢" instead of "B4 +17¢".

Original pitch estimate
Your method is correct. When A=450 Hz:
- Reed at 498.5 Hz = A4 + 23¢ sharp → ~452 Hz (since 450 Hz + 23¢ ≈ 452 Hz).
- Original pitch was likely ~452 Hz, common for pre-1940 European instruments.

My advice will be to
1. Ignore the app’s note name—focus on Hz and cents.
2. Tune reeds to modern pitch (A=440) unless you want historical accuracy.
3. For restoration, A=452 Hz matches your measurements.

Not your age this app behavior confuses many Trust your ear and Hz readings.

 

[Ventura]

ok, as an outsider (regarding Steirische 3 row in Bb/Eb/Ab)
what you are really asking is what SHOULD the reed frequencies be

your results are so far off the map it suggests this thing is
a hot mess and hey, can it even be brought back into some kind
of civilized compliance ?

seems to me the obvious way to get your bearings is simply to
ask someone who still builds these things to share with you
an actual factory tuning chart/tuning target that would be used
on a brand new Steirische 3 row in Bb/Eb/Ab

then you can simply look at it compared to your reeds and
easily decide whether they can be saved, or if you really
just need to ask that same factory to sell you a new set of reeds
and finish the rebuild while you are still young enough to enjoy it !

hehehe

good luck

 

[Glug]

Thanks Glug..

I took sets of readings, tried to get an average of where the cents deviations were and then increased the A4 standard. When I got to A4=450 the + and - cents deviations averaged near zero and that's when I thought this box must be tuned near 450. Your calculation confirms that. If the y axis is Hz what is the x axis?

What formula do I need to plug into the spreadsheet to perform this calculation myself on other reed banks in this box.

Thanks Again!

In my example the x axis is the "note number" in the A column.
B column is what we know it as (and a label for charts)

C,D,E are the tuning target if A4 was the row 3 value.

C4 = C$3 * 2^(($A4-6)/12-1)

The "-6" adjusts for where the A column numbering starts, and it's written that way so I can change octave by changing the "-1" to "-0" etc.
Easy way to get that right is to change the "-6" until you get A4 = 440.

So basically you want the E column with E3 set to 449:

 

[jollyrogeraccordions]

So, when I started out tuning (over ten years ago now), I'd try to determine the tuning scheme of a given instrument by measuring lots of reeds and averaging out, etc. But now I assume that if it's old and generally flat, it's probably 435, or if it's very sharp it'll be Old Philharmonic pitch, which is 454 (about a quarter tone sharp). If it's a modern Italian made box it could be 442, which is their default concert pitch unless you request otherwise. But in a way, it doesn't really matter because what's important is the target tuning. I have (laboriously) sharpened a few big accordions from somewhere around 435 to 440. It is a never ending job (nb: i've found the Petersen tuner actually ignores talk radio so it's possible to tune whilst taking the edge off the boredom by listening to something). I have also flattened english concertinas from 454 to 440 numerous times (it seems to be the default tuning on old ECs). What you actually need to know is how far and in which direction to shift a reed. If you just want it in tune with itself then pick reeds that don't get used very often to determine the reference pitch..they will be closer to the original tuned pitch. Then set your tuner. So, on (for instance) a BC diatonic box, many of the notes in the B row are rarely used. On a PA the bass reeds don't tend to shift so much so that's a good place to check to find the instrument's tuned pitch. In general PAs are tuned to equal temperament and so are the treble notes on a diatonic box, although E.g. Cajun boxes have optimised thirds and sevenths. So, don't overthink it. Check individual reeds in situ and tune them to your target pitch. And newish modern accordions tend to sharpen up a few cents, especially on the right hand. If the tuning is off on a heavily gigged PA, it does tend to go sharp a little bit, and then you have to do the trickiest bit of tuning, flattening small inside reeds, without messing up the voicing (the little gap).