Guide détaillé à venir
Nous préparons un guide éducatif complet pour le Chord Frequency Calculator. Revenez bientôt pour des explications étape par étape, des formules, des exemples concrets et des conseils d'experts.
The Chord Frequency Calculator computes the fundamental frequencies in Hertz (Hz) for every note within a musical chord, using the equal temperament tuning system. Equal temperament divides the octave into 12 equal semitones, with each semitone separated by a frequency ratio of the 12th root of 2 (approximately 1.05946). This system, standardized around A4 = 440 Hz, is the dominant tuning used in Western music for keyboards, fretted instruments, and modern digital instruments. Understanding chord frequencies is vital for audio engineers designing crossovers and EQ curves, synthesizer programmers building additive or subtractive patches, acousticians analyzing room resonances, and composers working with electronic instruments. A chord consists of three or more notes played simultaneously, and each note's frequency determines how it interacts with others through consonance and dissonance. The frequency relationships between notes in a chord define the emotional character of the chord — close-interval clusters create tension while wider intervals with simple frequency ratios (like octaves at 2:1 or perfect fifths at 3:2) sound open and stable. In equal temperament, perfect consonances like the fifth are slightly mistuned from their pure just-intonation ratios (the ET fifth is 1.4983 instead of the pure 1.5), but the tradeoff allows the same instrument to play in all 12 keys equally well. This calculator accepts a root note, octave number, and chord quality, then outputs the frequency of each chord member. It covers major, minor, dominant 7th, major 7th, minor 7th, diminished, augmented, and extended chords such as 9ths and 11ths, covering the full range of chord types used in jazz, classical, pop, and electronic music.
f(n) = 440 × 2^((n - 69) / 12) where n is the MIDI note number (A4 = 69) Or: f = f_root × 2^(semitones / 12)
- 1Step 1: Identify the root note and its octave (e.g., C4, A3, G#5).
- 2Step 2: Calculate the MIDI note number: n = 12 × (octave + 1) + pitch_class, where C=0, C#=1, D=2 ... B=11.
- 3Step 3: Convert MIDI note to frequency: f = 440 × 2^((n - 69) / 12).
- 4Step 4: Determine the chord intervals (semitone offsets) from the root based on chord quality.
- 5Step 5: Add each interval's semitone count to the root MIDI number and recalculate frequency for each chord member.
- 6Step 6: Display all note names and their frequencies in Hz.
C4 is MIDI 60: 440 × 2^((60-69)/12) = 261.63 Hz. E4 is 4 semitones up: 261.63 × 2^(4/12) = 329.63 Hz. G4 is 7 semitones up: 261.63 × 2^(7/12) = 392.00 Hz.
A3 = MIDI 57 = 220 Hz. Minor chord intervals: root (0), minor third (3 semitones) = C4 at 261.63 Hz, perfect fifth (7 semitones) = E4 at 329.63 Hz.
G3 = MIDI 55 = 196 Hz. Intervals: 0, 4, 7, 10 semitones. B3 = 196 × 2^(4/12) = 246.94 Hz. D4 = 196 × 2^(7/12) = 293.66 Hz. F4 = 196 × 2^(10/12) = 349.23 Hz.
F#4 = MIDI 66 = 369.99 Hz. Diminished intervals: 0, 3, 6 semitones. A4 = 440 Hz (3 semitones up). C5 = 523.25 Hz (6 semitones up).
Bb3 = MIDI 58 = 233.08 Hz. Major 7th intervals: 0, 4, 7, 11 semitones. The major seventh (11 semitones) lands on A4 at 440 Hz.
Synthesizer patch design and oscillator tuning — This application is commonly used by professionals who need precise quantitative analysis to support decision-making, budgeting, and strategic planning in their respective fields
Audio crossover frequency selection for speaker design — Industry practitioners rely on this calculation to benchmark performance, compare alternatives, and ensure compliance with established standards and regulatory requirements, helping analysts produce accurate results that support strategic planning, resource allocation, and performance benchmarking across organizations
Room acoustic resonance analysis and treatment — Academic researchers and students use this computation to validate theoretical models, complete coursework assignments, and develop deeper understanding of the underlying mathematical principles
Microphone placement to avoid room modes at chord frequencies. Financial analysts and planners incorporate this calculation into their workflow to produce accurate forecasts, evaluate risk scenarios, and present data-driven recommendations to stakeholders
Digital instrument design and virtual instrument programming — This application is commonly used by professionals who need precise quantitative analysis to support decision-making, budgeting, and strategic planning in their respective fields
Enharmonic Equivalents
{'title': 'Enharmonic Equivalents', 'body': 'In equal temperament, C# and Db are the same frequency (277.18 Hz at octave 4). The naming depends on musical context and key signature, but the physical frequency is identical.'} When encountering this scenario in chord frequency calc calculations, users should verify that their input values fall within the expected range for the formula to produce meaningful results. Out-of-range inputs can lead to mathematically valid but practically meaningless outputs that do not reflect real-world conditions.
Octave Doublings
If G3 = 196 Hz, then G4 = 392 Hz and G5 = 784 Hz. Stacking octaves adds fullness without adding harmonic complexity.'} This edge case frequently arises in professional applications of chord frequency calc where boundary conditions or extreme values are involved. Practitioners should document when this situation occurs and consider whether alternative calculation methods or adjustment factors are more appropriate for their specific use case.
Microtonal Chords
{'title': 'Microtonal Chords', 'body': 'Some contemporary music uses microtonal tuning systems with more than 12 divisions per octave. In 24-TET, there are 24 equal divisions, and chord frequencies are calculated using 2^(1/24) per step instead of 2^(1/12).'} In the context of chord frequency calc, this special case requires careful interpretation because standard assumptions may not hold. Users should cross-reference results with domain expertise and consider consulting additional references or tools to validate the output under these atypical conditions.
| Chord Type | Intervals (semitones) | Example (root C) |
|---|---|---|
| Major | 0, 4, 7 | C, E, G |
| Minor | 0, 3, 7 | C, Eb, G |
| Diminished | 0, 3, 6 | C, Eb, Gb |
| Augmented | 0, 4, 8 | C, E, G# |
| Dominant 7th | 0, 4, 7, 10 | C, E, G, Bb |
| Major 7th | 0, 4, 7, 11 | C, E, G, B |
| Minor 7th | 0, 3, 7, 10 | C, Eb, G, Bb |
| Major 9th | 0, 4, 7, 11, 14 | C, E, G, B, D |
| Minor 9th | 0, 3, 7, 10, 14 | C, Eb, G, Bb, D |
| Sus2 | 0, 2, 7 | C, D, G |
| Sus4 | 0, 5, 7 | C, F, G |
Why is A4 = 440 Hz the standard reference pitch?
A4 = 440 Hz was internationally standardized by the International Organization for Standardization (ISO) in 1955 and confirmed by ISO 16:1975. Before standardization, pitch varied widely — Baroque ensembles often tuned to A=415 Hz, and some orchestras in the 19th century used A as high as 452 Hz. The 440 Hz standard allows instruments from different manufacturers and musicians from different countries to play together in tune. Some orchestras (notably in Berlin and Vienna) tune to A=442 or A=444 Hz for a brighter sound.
What is equal temperament and why does it matter?
Equal temperament (ET) divides the octave into 12 equal logarithmic steps. Each semitone has a frequency ratio of 2^(1/12) ≈ 1.05946. This means every key sounds equally in tune (or equally out of tune, depending on perspective). Before ET, instruments were tuned in various systems like meantone or Pythagorean tuning, which were more consonant in some keys but unusable in others. ET allows a piano to play equally well in C major and F# major, which is essential for Western classical and pop music.
What is the difference between a major and minor chord in terms of frequencies?
A major chord uses intervals of 0, 4, and 7 semitones from the root (major third + perfect fifth). A minor chord uses 0, 3, and 7 semitones (minor third + perfect fifth). The only difference is one semitone in the middle note, but this dramatically changes the emotional character. The major third (4 semitones) has a frequency ratio of approximately 1.26, while the minor third (3 semitones) has a ratio of approximately 1.189. This subtle difference in ratio is what gives major chords their 'bright' quality and minor chords their 'darker' quality.
How do overtones relate to chord frequencies?
Every musical note produces overtones (harmonics) at integer multiples of the fundamental frequency. When two notes in a chord share overtones, they sound consonant. For example, C4 (261.63 Hz) and G4 (392 Hz) share an overtone near 784 Hz (G4's second harmonic). The closer the frequency ratio of two notes is to a simple integer ratio, the more overtones they share and the more consonant they sound. Equal temperament approximates these simple ratios, which is why chords work well even though ET intervals are slightly detuned from pure mathematical ratios.
Can I use this calculator for non-standard tunings like A=432 Hz?
Yes. If your reference pitch is not A4=440 Hz, you can scale all frequencies by the ratio of your reference to 440. For A=432 Hz, multiply all 440-based frequencies by 432/440 = 0.9818. Every note and chord frequency shifts proportionally. While A=432 Hz has a devoted following who believe it is more harmonious with nature, there is no scientific acoustics research supporting perceptual benefits over 440 Hz — the difference is only about 32 cents, less than a third of a semitone.
How do chord frequencies help in audio mixing and EQ?
Knowing the fundamental frequencies of chord members helps engineers identify problematic resonances. If a guitar chord rings out with uncomfortable boominess, checking the frequencies of its root and fifth helps pinpoint which EQ bands to cut. Mastering engineers use harmonic frequency knowledge to decide where to apply gentle boosts or cuts without disrupting the tonal balance of chords. Synthesizer sound designers use chord frequencies to tune oscillators, set filter cutoffs at harmonically relevant points, and build chords from individual sine waves in additive synthesis.
What is the frequency of middle C?
Middle C, designated C4 in scientific pitch notation (also called C4 in MIDI where C-1=0), has a frequency of approximately 261.626 Hz in standard equal temperament at A4=440 Hz. It is MIDI note 60. Middle C is significant as the approximate center of the piano keyboard, the typical boundary between treble and bass clef in piano music, and a common reference point in acoustics and music theory discussions.
Why do some chords sound dissonant even though all notes are in tune?
Dissonance arises from the interaction of overtones rather than from being 'out of tune.' When two notes have a complex frequency ratio with many non-matching overtones, they create beating patterns — rapid amplitude fluctuations audible as a rough, tense sound. For example, a tritone (6 semitones, ratio ≈ 1.414) produces many clashing overtones, creating its characteristic tension. This tension is a compositional resource, not a flaw — dissonance creates emotional intensity and makes resolution to consonant chords feel satisfying.
Conseil Pro
When designing synthesizer patches, try detuning oscillators by a few cents from perfect chord frequencies to create chorus-like beating between oscillators. This is the secret behind the thick, lush sound of classic Juno and Jupiter synthesizers.
Le saviez-vous?
The frequency ratio of a perfect fifth in equal temperament is 2^(7/12) ≈ 1.4983, compared to the pure just-intonation ratio of 3/2 = 1.5. This difference of about 2 cents (0.02 semitones) was considered a significant compromise when equal temperament was first widely adopted in the 18th century, sparking heated debates among music theorists.