Rubber Band Library is a high quality software library for audio time-stretching and pitch-shifting. It permits you to change the tempo and pitch of an audio stream or recording dynamically and independently of one another.
dca91fbd08ed — Chris Cannam rblive tip 9 days ago
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381b6368a553 — Chris Cannam 11 days ago
Adjust test check
feb19ac31aa0 — Chris Cannam 16 days ago
Adjust start delays, put an end point on sinusoid


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#Rubber Band Library

An audio time-stretching and pitch-shifting library and utility program.

Written by Chris Cannam, Published by Particular Programs Ltd t/a Breakfast Quay. Copyright 2007-2024 Particular Programs Ltd.

Rubber Band is a library and utility program that permits changing the tempo and pitch of an audio recording independently of one another.

CI builds:

  • Build status (Linux)
  • Build Status (macOS, iOS)
  • Build Status (Windows)


Rubber Band Library is distributed under the GNU General Public License (GPL). You can redistribute it and/or modify it under the terms of the GPL; either version 2 of the License, or (at your option) any later version. See the file COPYING for more information.

If you wish to distribute code using Rubber Band Library under terms other than those of the GNU General Public License, you must obtain a commercial licence from us before doing so. In particular, you may not legally distribute through any Apple App Store unless you have a commercial licence. See for licence terms.

If you have obtained a valid commercial licence, your licence supersedes this README and the enclosed COPYING file and you may redistribute and/or modify Rubber Band under the terms described in that licence. Please refer to your licence agreement for more details.

Rubber Band includes a .NET interface generously contributed by Jonathan Gilbert under a BSD-like licence. The files in the dotnet/rubberband-dll and dotnet/rubberband-sharp directories fall under this licence. If you make use of this interface, please ensure you comply with the terms of its licence.

Rubber Band may link with other libraries or be compiled with other source code, depending on its build configuration. It is your responsibility to ensure that you redistribute these only in accordance with their own licence terms, regardless of the conditions under which you are redistributing the Rubber Band code itself. The licences for some relevant library code are as follows, to the best of our knowledge. See also the file for more details.

  • FFTW3 - GPL; proprietary licence needed for redistribution
  • Intel IPP - Proprietary; licence needed for redistribution
  • SLEEF - BSD-like
  • KissFFT - BSD-like
  • libsamplerate - BSD-like from version 0.1.9 onwards
  • Speex - BSD-like
  • Pommier math functions - BSD-like

#Compiling Rubber Band Library

Please refer to the file for details of how to configure and build the library.

#Contents of this README

  1. Code components
  2. Using the Rubber Band command-line tool
  3. Using Rubber Band Library

#1. Code components

Rubber Band consists of:

  • The Rubber Band Library code. This is the code that will normally be used by your applications. The headers for this are in the rubberband/ directory, and the source code is in src/. The Rubber Band Library may also depend upon external resampler and FFT code, if so configured; see section 7 of for details.

  • The Rubber Band command-line tool. This is in main/main.cpp. This program uses Rubber Band Library and also requires libsndfile (, licensed under the GNU Lesser General Public License) for audio file loading.

  • A pitch-shifter audio effects plugin in LADSPA and LV2 formats. These are in ladspa-lv2/. They require the LADSPA SDK header ladspa.h and LV2 header lv2.h respectively (not included).

  • A Vamp audio analysis plugin which may be used to inspect the dynamic stretch ratios and other decisions taken by the Rubber Band Library when in use. This is in vamp/. It requires the Vamp plugin SDK ( (not included).

#2. Using the Rubber Band command-line tool

The Rubber Band command-line tool builds as build/rubberband. The basic incantation is

  $ rubberband -t <timeratio> -p <semitones> <infile.wav> <outfile.wav>

For example,

  $ rubberband -t 1.5 -p 2.0 test.wav output.wav

stretches the file test.wav to 50% longer than its original duration, shifts it up in pitch by a whole tone, and writes the output to output.wav.

Several further options are available: run rubberband -h for help.

The most important are the options -2 and -3. These select between two different processing engines, known as the R2 (Faster) engine and the R3 (Finer) engine. The R3 engine produces higher-quality results than R2 for most material, especially complex mixes, vocals and other sounds that have soft onsets and smooth pitch changes, and music with substantial bass content. However, it uses much more CPU than the R2 engine.

The R2 engine was the only method available in Rubber Band Library up to versions 2.x, and for compatibility it remains the default (in the case that neither -2 nor -3 is requested explicitly) whenever the command-line tool is invoked as rubberband. The R3 engine is the default if the tool is invoked as rubberband-r3.

Many further options are available, most of which only have an effect when using the R2 engine. In particular, different types of music may benefit from different "crispness" options (-c flag, with a numerical argument from 0 to 6).

#3. Using Rubber Band Library

Rubber Band has a public API that consists of one C++ class, called RubberBandStretcher in the RubberBand namespace. You should #include <rubberband/RubberBandStretcher.h> to use this class. There is extensive documentation in the class header.

A header with C language bindings is also provided in <rubberband/rubberband-c.h>. This is a wrapper around the C++ implementation, and as the implementation is the same, it also requires linkage against the C++ standard libraries. It is not yet documented separately from the C++ header. You should include only one of the two headers, not both.

A .NET interface is also included, contributed by Jonathan Gilbert; see the files in the dotnet directory for details.

The source code for the command-line utility (main/main.cpp) provides a good example of how to use Rubber Band in offline mode; the pitch shifter plugin (ladspa-lv2/RubberBandPitchShifter.cpp) may be used as an example of Rubber Band in real-time mode.

IMPORTANT: Please ensure you have read and understood the licensing terms for Rubber Band before using it in your application. This library is provided under the GNU General Public License, which means that any application that uses it must also be published under the GPL or a compatible licence (i.e. with its full source code also available for modification and redistribution) unless you have separately acquired a commercial licence from the author.

#4. Further documentation