Method, measured accuracy and sources

What Sing is

Sing is a vocal pitch monitor with a target-note mode, a vocal range test, exercises for singing scales and singing intervals against a reference, and pitch matching by ear. Any song in the labs.llc song book (five lists, 5,018 tracks) can be sent to it with Sing this. It is free, has no accounts, and is part of labs.llc, in the Sound room beside the chromatic tuner, which reads instruments. It was sing.com.im until 2026; every address there now answers one permanent redirect to its page here.

It reports pitch. It is not vocal coaching and not medical advice, and it makes no claim about what singing with it will do for a voice.

How the pitch is found

Up to 30 times a second the page takes the most recent block of sound from the microphone, 4,096 samples or about 85 to 93 thousandths of a second, and looks for the period at which the block repeats. The method is the normalised square difference function described in McLeod and Wyvill, “A Smarter Way to Find Pitch”: the block is compared with a shifted copy of itself at every shift in the search range, and the result is scaled so that a perfectly repeating sound scores 1. That score is the clarity figure the page prints.

The shift chosen is the first peak that reaches 85% of the tallest one, not the tallest, because the tallest is often at twice the true period and would name the octave below. The peak is then re-measured on a shorter, more recent slice of the block, so that a moving pitch is measured where it is now, and refined between samples with a parabola. A block quieter than −48 dBFS, or with a clarity under 0.55, is given no pitch.

Frames then pass through a tracker. A note has to begin with a clarity of at least 0.8 and may continue down to 0.55. The first frame of a note is held until a second agrees with it. A frame more than 350 cents from the ones before it is not believed until three frames in a row agree. The trace draws every frame that passes. The note name, the cents figure and the timers use the centre of the last nine frames: the midpoint, in cents, between the lowest and the highest of them.

The detector is the trainer’s own: it began as the tuner’s and was changed for a voice (a narrower range, two passes, a tracker that allows vibrato), so the two are separate files measured separately.

Your microphone and your privacy

The microphone opens only when you press Start microphone, and closes when you press it again, leave the page or put the tab in the background. The browser’s echo cancellation, noise suppression and automatic gain are asked to stay off, because all three reshape a held note.

The sound is handed to an analyser inside the page and to nothing else. It is not played back, not recorded, not stored and not sent: the trainer’s scripts make no network request of any kind with it, and each block of sound is overwritten by the next. What is kept is in this browser’s own storage: the A4 reference (labs.sing.a4), the choice of note names (labs.sing.solfege) and the lowest and highest notes from the range test (labs.sing.range). The paper or dark edition you chose is kept under labs_edition, in local storage and in a cookie. Clearing the site’s data in your browser removes them all. Settings saved on sing.com.im before the trainer moved here stay in that site’s storage: a browser keeps each site’s storage apart.

When a song is named on the trainer, the page loads that list from the labs.llc song book, a file on labs.llc. The links marked Find on YouTube and Find on Spotify are ordinary links: nothing is asked of those sites unless you press one, and then it opens in a new tab.

Analytics. labs.llc counts visits with Google Analytics, the one script on the page that talks to anyone else, and only from labs.llc itself. It is told which page was opened and in which edition, and, as on every labs.llc tool, that one of the page’s controls was first used, that the page was in use for thirty seconds, and how quickly the page drew and answered (its LCP, CLS and INP timings, with the tag and the id or class of the element involved, never its text). The trainer’s own scripts tell it nothing: no sound, no note and no reading is part of any of it. The menus, the search and the Lab Assistant around the trainer are labs.llc’s own; the site’s legal page has the privacy note for all of labs.llc.

Settings

A4 can be set from 415 to 466 Hz and is 440 Hz by default, the standard tuning pitch (Wikipedia, A440 (pitch standard)). Notes are named with a letter and an octave number, with middle C as C4 (Wikipedia, Scientific pitch notation), and sharps are always written as sharps: the page hears a pitch, not a key, and cannot know whether a note is an F sharp or a G flat. Solfège names are fixed do, in which Do is always C (Wikipedia, Solfège). Cents are hundredths of an equal-tempered semitone (Wikipedia, Cent (music)).