How we get it right

Spellings are derived from the rules, not typed from a table

The 1,400+ chord and scale pages are not hand-written. A single music-theory engine spells every note the way a theory textbook would — one letter name per scale degree where possible, chord tones stacked in thirds, a single accidental preferred over a double. So C minor 7 is spelled C E♭ G B♭, never C D♯ G A♯, because the engine follows the same logic a person would.

An automated test suite checks it on every change

• 54 checks on the theory engine: known spellings (C major, F♯ major, D♭ major, the altered scale, the diminished scales…), then an exhaustive pass over every one of the 17 roots against every chord and scale type confirming no note needs a double accidental where a single one exists, and that all twelve pitch classes are covered.
• 197 checks on the diagrams: every guitar and ukulele chord shape is played back note-for-note and compared against the engine — a shape that would sound a wrong note fails the build.
• Both suites run inside npm run build. If a single check fails, the build stops and nothing is deployed. This is not optional and cannot be skipped.

This has already paid off: the test suite caught two movable guitar shapes (9 and add9) that had been copied from the m7 shape and would have sounded a wrong note. They were removed the same day.

The maths is objective and standard

A metronome, a tuner and a chord player have nothing to prove — the formulas are fixed and universally agreed:

• Metronome: the gap between beats is 60000 / BPM milliseconds. Timing is scheduled through the Web Audio clock, not setTimeout, so it does not drift.
• Tuner & virtual piano: concert pitch A4 = 440 Hz, equal temperament — a note n semitones from A4 is 440 × 2^(n/12) Hz.
• Everything you hear plays in your browser. No audio, no microphone input and no practice data is ever sent to a server. Most tools generate their click or tone directly; the piano, Turkish makam, and ear-training tools instead play real recorded piano and violin notes, pitch-shifted to the exact note — or, for makam, the exact microtonal pitch — needed. The recordings are served from our own servers, never a third-party audio CDN.

Sample credits

The piano and violin recordings are University of Iowa Electronic Music Studios samples, packaged for the web by the tonejs-instruments project and used under CC BY 3.0. Playback runs on Tone.js (MIT licensed).

Written from named reference works

The 360 Studio guides are written from standard university-level texts, not from Wikipedia. The core references are:

• Harmony & theory: Kostka & Payne, Tonal Harmony; Aldwell & Schachter, Harmony and Voice Leading; Laitz, The Complete Musician; Schoenberg, Theory of Harmony and Fundamentals of Musical Composition; Hindemith, The Craft of Musical Composition; Open Music Theory.
• Counterpoint: Fux, Gradus ad Parnassum; Bach chorale practice.
• Orchestration: Adler, The Study of Orchestration; Kennan, The Technique of Orchestration; Rimsky-Korsakov and Berlioz, Principles of Orchestration / Treatise on Instrumentation.

History and genre lessons draw on institutional sources (conservatoire syllabi, published scholarship, primary recordings), and artist and song studies cite the specific records they discuss.

94 songs, every key checked by hand

The song examples are not scraped from a crowd-sourced tab site. Each of the 94 entries was chosen for what it teaches, and its key and Roman-numeral analysis were verified by hand. An earlier version had 110 songs; it was cut to the ones we could stand behind, then rebuilt carefully to 94. If a progression is labelled I–V–vi–IV in G major, it is.

Cross-checked against more than one source

Where a page states a fact that is not pure theory — the reference tune for an interval, the songs associated with an alternate guitar tuning, a piece of history — it was checked against multiple independent sources before publishing, and corrected where the common version turned out to be wrong.

Where the answer is an estimate, we say so

• Live chord detection (the tool that listens through your microphone) is a best-effort estimate from the sound in the room. Treat it as a starting point, not a verdict — it can be thrown off by noise, distortion or a thick voicing.
• The chord and scale reference is complete for common practice, not exhaustive: it covers 27 chord types and 25 scale types across every key. Turkish makam has its own interactive page for the Arel-Ezgi-Uzdilek system and twenty makams plus the transposed şed makams — given in the standard conservatory form, with the genuine theoretical debates flagged on the page. Turkish usul covers the seven most-taught rhythmic cycles, each pattern cross-checked against more than one source and verified to sum to its stated zaman count. Turkish instruments covers the five core voices of the fasıl ensemble — where sources gave conflicting or unconfirmed numbers (an exact string count, an exact tuning), we describe the instrument in general terms rather than publish a figure we could not confirm. Other microtonal traditions (raga, gamelan tunings) are covered in the lessons but not yet as interactive tools.

Tell us — we fix fast

Cloud Atelier is an independent music-education project. Everything on it is free to use with no account and no ads. See the tools, the guides, or the chord & scale reference.