About

This is not a standard playback speed adjuster. This is a harmonic transposition engine designed for vocalists, producers, and audio engineers who demand tonal accuracy. While basic tools simply stretch the audio file - destroying the timing and attack transients - this application utilizes a Granular Overlap-Add (OLA) algorithm with Phase Alignment. This decouples the pitch domain from the time domain, allowing you to change the key of a song without altering its tempo, or correct the tuning of a sample by mere cents.

Precision is paramount in musical applications. A shift of just 10 cents can make a vocal track feel "flat" or "sharp" in a mix. This tool provides distinct processing modes: Melodic Mode for monophonic sources (vocals, bass) where preserving the fundamental frequency is critical, and Polyphonic Mode for complex mixes (full songs) to minimize phase cancellation. The integrated real-time Fast Fourier Transform (FFT) visualizer confirms that your target frequencies are hit with mathematical precision.

Formulas

To achieve accurate pitch shifting, we calculate the transposition factor k based on the desired semitone shift s and fine-tuning in cents c. The formula utilizes the logarithmic nature of musical perception:

k = 2^{s + (c / 100)12}

When correcting for formants (timbre preservation), we estimate the spectral envelope shift required. If the fundamental frequency f₀ shifts to f_new, the formant peaks F_n must remain at their original absolute frequencies to preserve the "identity" of the voice. The phase increment φ for the granular engine is derived as:

Δφ = 2π × f_targetf_sampleRate

Reference Data

Note (Scientific)	Frequency (Hz)	Interval Shift	Ratio (r)	Wavelength (cm)
C0	16.35	Octave -4	0.0625	2109.89
C1	32.70	Octave -3	0.1250	1054.94
C2	65.41	Octave -2	0.2500	527.47
C3	130.81	Octave -1	0.5000	263.74
A3	220.00	Perf 5th Down (-7 st)	0.6674	156.82
C4 (Middle C)	261.63	Original Root	1.0000	131.87
A4 (Concert)	440.00	Major 6th Up (+9 st)	1.6818	78.41
C5	523.25	Octave +1	2.0000	65.93
C6	1046.50	Octave +2	4.0000	32.97
C7	2093.00	Octave +3	8.0000	16.48
C8	4186.01	Octave +4	16.0000	8.24

Frequently Asked Questions

A semitone is the smallest standard interval in Western music (e.g., the distance from C to C#). A cent is a logarithmic unit of measure used for musical intervals. There are 100 cents in one semitone. Use the "Semitone" slider for changing keys, and the "Cents" slider for fine-tuning out-of-tune audio or matching non-standard tunings like 432Hz.

Formant correction keeps vocals sounding natural by preserving the throat resonance. However, if you are pitching instruments (like a guitar or synth) or sound effects, formant correction might introduce unwanted blurring. Turn it off for a cleaner, crispier sound on non-vocal tracks.

Stuttering usually occurs if the "Grain Size" is too large for the content, or if the browser's CPU is overloaded. Try enabling "Low Latency Mode" or reducing the grain size. For rhythmic tracks (drums), a smaller grain size (20-40ms) is often better to preserve transients.

Yes. The output is a high-fidelity WAV file (Lossless). The algorithm runs locally in your browser, so there is no audio compression or quality loss associated with server uploads. What you hear is exactly what you get.

Yes, but be aware that real-time granular synthesis is CPU-intensive. Newer smartphones (iPhone 12+, High-end Androids) handle it well. On older devices, we recommend using the "Preview" mode for short durations and then using the "Render" button to process the full file offline.