The vocabulary
A few words do a lot of work here. They are the trade's, not ours.
Reed (voice)
One vibrating tongue, głos in Polish. A single note can sound several reeds at once, and each one is tuned on its own.
Register, banks and feet
A register is what a switch turns on. The banks are the ranks of reeds inside the box: L (16', an octave below the key), M1 / M2 / M3 (up to three 8' ranks at concert pitch) and H (4', an octave above). A register is its reed count, so LMMM sounds four reeds.
Beating (tremolo)
Two reeds a little apart beat at their difference in hertz, and that pulsing is the tremolo, the musette sound, dudnienie in Polish. Tuning a musette is not making it zero: a wide beat there is correct, and a tuner that paints it red is lying.
The beating curve
What the tremolo should be, note by note. Without it the app can only tell you how far a reed sits from the bare scale, not whether it is right. You draw the curve, or fit it to the instrument's own recording.
A pass
One trip through the instrument, everything caught in a single sitting. Its A4 reference is frozen at the start, because a pass measured against a moving reference is worthless.
Bellows direction
Every note has two reeds: one that sounds on the press, one on the draw. They are different tongues on opposite faces of the same plate, both of them tuned, and they drift apart on their own. You set the direction and the recorder stamps it on every reading, so the card can say which of the two a number belongs to. This is true of every accordion, not only a button box.
The control appears once a session is open, because the direction is something a session records; there is nothing to stamp without one.
Bisonoric is a separate thing. On a diatonic button box a key sounds a different note pushing than pulling. That changes what you play, not whether the direction is worth recording.
The merged pair
Low on the keyboard a musette pair can sit too close to split into two peaks. When it does, SmeggTuner shows the one honest reading, the beat between them, and prints no separate reed numbers instead of inventing a plausible wrong one. A missing number costs nothing; a wrong one costs a reed.
Why the numbers behave as they do
Three facts about reeds decide the whole shape of the app. They are worth two minutes now.
A beat is a difference, so it survives what moves both reeds together. Press the bellows harder and a reed's pitch falls, worst down low. But both reeds of a pair fall together, so the beat between them barely moves. Absolute pitch has to be measured at playing pressure. The tremolo is forgiving.
The ear hears beats far better than pitch. A note has to be about 2 Hz out before anyone notices it in a melody. A change in beat rate of a tenth of a hertz is audible to a trained tuner. So the beat between two reeds must be held tighter than either reed's own pitch: if both are three cents sharp, the tremolo is still perfect and nobody hears a thing.
A reed's pitch depends on the box it sits in. Open the accordion and it changes. Lift the reed block out and it changes again. Put everything back and it changes back. The difference runs to about three cents, which is three times the tolerance a good technician works to.
That last one is why the workflow below is shaped the way it is, and why you do not file to zero on the bench.
The workflow it is built around
A reed's pitch changes the moment you open the accordion and pull the block out, so you cannot measure, file, and measure again in one motion. The app is built for the way the job is really done.
- Record a pass, box closed. With the instrument closed and playing normally, record every note. That is a pass.
- Read the errors. For each reed the table shows its current pitch, its goal, and the error between them, judged against your tolerance.
- Open the box once, file by the numbers. Open the accordion a single time and file each reed by its error. No guessing, no back and forth.
- Record again and compare. Close it, record a second pass, and lay it over the first: what improved, what got worse, what is done.
The three rooms
One window, three rooms, and a key each. Nothing scrolls.
Tune
The microphone is open and the needle moves. Read it top to bottom: the input trace and level, a note strip across the whole range (E0 to C9), the spectrum of the detected tone beside a large note readout, the ruler with a needle per reed, and a value box per reed. Auto follows the played note; manual pins one so you can work it.
The toolbar carries start and stop, the source, auto or manual, the note and octave steppers, freeze, note sounds, the register, the bellows direction, record and undo.
Workshop
Sessions, instruments, and the cards you print. An instrument is described once and used for every session on it. A session is one job on one accordion.
Settings
The input device, the deviation unit, the naming, the behaviour of the reading, and the look of the app. The reference pitch is not here: it belongs to the instrument.
Leaving the Tune room stops the tuner, whichever door you leave by. That is deliberate: the engine holds the microphone open and runs a DSP pipeline twelve times a second, and none of that is doing anything for someone reading a table. It costs one keypress to come back and it costs nothing else. Stopping the engine does not end an open pass and does not disarm recording, so pressing Start on the way back in goes on filling the same pass with nothing lost. Calibration is the one exception: it is guided tuning, so the microphone stays live there.
Sources
Two: a microphone, or a WAV file. A loaded file behaves like a recording - a transport in the header, a waveform you scrub and zoom, and a selection you drag over the steady middle of a note. The selection is the loop, and the range you select is the range that gets measured.
Reading the tuner
Colour means something here, or it is not there. Three hues carry the reading, one meaning each:
A measured reed: its needle, its frequency, the spectrum trace.
The goal: the target line on the ruler, the figure under each box, the beat curve.
Outside tolerance: a reed value, a table cell, a graph mark. It shows only when the app has judged the reed out, never as decoration.
Beside them there is one blue accent, and it means "here" and "do this" - the button you press, the room you are in, a link. Nothing else on screen gets a colour at all.
Each value box is named for what it holds - Reed 1, Beat 1 to 2, Reed 2 - and carries an error bar that grows out of the centre. The centre is the goal, so the bar is the error itself: left for flat, right for sharp, length for how far. Two notches mark tolerance, four tolerances wide, so a reed in cents and a beat in hertz read the same way.
The recorded table goes further and names its columns by rank (L, M1, M2), because there the register that was pulled is known. On the tuner it is not, so the boxes count instead of guessing.