You can freely build on How Real-Time Pitch Correction and Auto-Tune Technology Works

What this patent covers

This patent describes a digital signal processing method that identifies the fundamental frequency of a voice or instrument by sampling audio and calculating its period. It uses an auto-correlation function—a mathematical way to find repeating patterns in a signal—to determine the pitch. Once the pitch is identified, the system calculates the difference between the current note and a target note from a musical scale or MIDI input. It then resamples the audio waveform to shift its frequency, effectively correcting the intonation of the performance.

What is now free to use

All 0 claims of US 5973252 are in the public domain. Specifically:

The 0 dependent claims add narrowing limitations and are also free.

What is NOT covered

Patent expiry frees this specific invention. Separately-patented improvements made after expiry may still be protected.

• Does not cover non-digital or analog-only pitch correction methods.

• Does not cover methods that rely on frequency domain analysis like Fast Fourier Transforms (FFT).

• Does not cover non-real-time pitch correction performed on pre-recorded audio files.

• Does not cover vocal synthesis or generating new notes from scratch.

Who is building on this today

Companies like Antares Audio Technologies, Celemony, and Waves Audio have built extensive product ecosystems based on these fundamental principles of real-time pitch detection and manipulation. The industry has since evolved to include more sophisticated spectral analysis, but the core concept of period-based resampling remains a staple in audio engineering.

Products built on expired version of this technology

How to cite this patent in your documentation

Auburn Audio Technologies Inc. US Patent 5973252. Pitch detection and intonation correction apparatus and method. Granted 1999, expired 2018. Now in the public domain.

Note: This is a convenience citation. Consult a patent attorney for formal freedom-to-operate analysis.

PatentBrief is an educational resource and does not provide legal advice. Patent expiration information is derived from USPTO records and may not reflect continuation patents, divisional filings, or separately-patented improvements. For commercial use or production decisions, obtain a formal freedom-to-operate (FTO) opinion from a registered patent attorney.