Your tuner does not know what key you are in

A tuner asks one question. Where does this note sit against equal temperament? It answers in a tenth of a second, and the answer is right.

It has never asked what key you are playing in, and a doctoral thesis on double bass intonation spends a chapter explaining why that question comes first.

A note becomes judgeable once the key is clear

The thesis assembles the psychology and acoustics literature into one claim: intonation is discriminated best when the tonal plan is clear and the key has taken hold.

Turn that around. When the key is unclear, a listener has to switch schemas to find a home for the note they just heard. Switching costs time, and the verdict on whether the note was in tune arrives in retrospect, after the note has gone. In a stable key, the judgment lands at once.

The key is the condition that makes the measurement mean something, and without it you have a number with nowhere to sit.

And the tonic does a specific job while you play. Five separate researchers, working on singers, cellists and violinists, have found that players hold the tonic active and compare against it. Your ear is already running the reference the tuner has never been told about.

The same note asks for different precision

The first, the fourth and the fifth degree are close relatives in sound and in function, and players hold them to tighter tolerances than a degree like the sixth, which can mean several things depending on where the music is going.

One researcher wrote string quartets for the purpose of testing this and found that the load-bearing intervals came back with very low dispersion, the tonic most of all. In the pieces he built with an ambiguous tonic on purpose, the implied tonic still drifted by a few cents and no further. Studies on singers and on cellists found the same ordering in performance: the first, fourth and fifth degrees held near the sizes that pure ratios give them, and the rest given room.

Take one A. In A major it is the tonic, the note everything else is measured from, and it gets almost no room. In D major it is the fifth, still structural, still tight. In C major it is the sixth degree, which the research says is the loosest of the set.

Same string, same finger, three different demands. A tuner shows you the same number three times.

What we do with that

You tell wabetune two things before you play: your reference A, and the tuning system with its tonic. From then on it measures every note against that target rather than against the piano. Declare a tonic and just intonation, play a pure major third, and the app reads zero rather than thirteen cents flat, because thirteen cents under equal temperament is where that third lives.

That is the part we have built. The next part we have not.

Nothing in the app yet knows that your tonic deserves more precision than your sixth degree. One tolerance covers every note on the map, which is the same assumption the tuner makes, at a better target. The research says the assumption is wrong. Fixing it means the report has to weight a note by its function and not by its distance alone, and we would rather say so than ship a claim we have not earned.

What the thesis is, and is not

It measured nobody. The author read the acoustics, the psychoacoustics and the cognition literature, derived a system for placing notes on a double bass from the resonance of its open strings, and tested it on paper against eight orchestral excerpts. The findings about scale degrees come from the studies he cites, not from work he ran.

He also wrote, about a community that leans on electronic tuners, that a tuner turns an aid into a crutch, and that he keeps meeting musicians whose ears have been carried off by the swing of the needle without ever building an independent sense of what being in tune means. We take the warning as pointed at us too. What we can defend is the target we measure against, and the fact that we keep the numbers instead of throwing each one away as the next one arrives.

Source: John Michael Priester, “Double Bass Intonation: A Systematic Approach to Solo and Ensemble Playing”, doctoral thesis, Jacobs School of Music, Indiana University, 2015.