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JSFX SoX Plugins for Reaper DAW


The JSFX-SoX software package provides JSFX (Jesusonic) plugins for being used in the Reaper DAW; they implement some of the audio processing effects from SoX. It is also possible to use them in any VST compatible DAW using the freely available ReaJS VST plugin that is able to interpret JSFX files.

SoX is a command line audio processing tool for Unix, Windows and Mac OS that transforms source audio files in several formats into other audio files.

The effects provided here are a complete rewrite of the SoX algorithms for producing (bit-exact) identical renderings in the DAW. This can easily be checked by rendering some audio externally with SoX and internally with the plugins and subtracting the results. Apart from roundoff errors (SoX often uses 32bit integer processing, while JSFX always uses double floating point processing) the results cancel out with typically a residual noise of -140dBFS.

The main motivation for this package is to be able to play around with effects in Reaper and be sure that the external rendering by SoX will produce exactly the same results. Although SoX does not always provide the "best" effects, it still is a reliable and well-defined audio tool.

Because SoX has rich command line options for its effects, not every effect configuration from SoX can be transported into the slider oriented GUI for JSFX. E.g. the compander of SoX allows the definition of a transfer function having multiple segments. Although the internal engine of the JSFX compander implements exactly the same internal segment logic, the user interface only allows the typical definition of a threshold and a compression ratio (with three segments).

Note also that a spiffy user interface is not at all a priority in this project.

The SoX effects have been rewritten and restructured for easier maintenance, because in the original source there is some redundancy and unnecessary complexity due to its several contributors. Nevertheless the effects provided here faithfully model the SoX processing.

Available Effects

The following effects are available in this package:

  • allpass: a biquad allpass filter two-poled with filter frequency and the filter bandwith (in several units)

  • band: a biquad bandpass filter with center filter frequency and the filter bandwith (in several units) and an option for unpitched audio

  • bandpass/bandreject: a biquad filter for bandpass or bandreject with center filter frequency and the filter bandwith (in several units)

  • bass/treble: a biquad filter for boosting or cutting bass or treble with a shelving characteristics with settings for filter frequency and the filter bandwith (in several units)

  • biquad: a generic biquad (iir) filter with 6 coefficients b0, b1, b2, a0, a1 and a2

  • compand: a compander with attack, release, input gain shift, threshold and compression and soft knee; this is a reduced version of SoX compand with only a simple transfer function

  • equalizer: a biquad filter for equalizing with settings for the pole count, the filter frequency and the filter bandwith (in several units)

  • gain: a volume changer by exact decibels...

  • lowpass/highpass: a biquad filter for either lowpass or highpass with settings for the pole count, the filter frequency and the filter bandwith (in several units)

  • mcompand: a multiband compander with a Linkwitz-Riley crossover filter and for each band a compander with attack, release, input gain shift, threshold and compression and soft knee; again the companders only allow a simple transfer function

  • overdrive: a simple tanh distortion with gain and colour specification

  • phaser: a phaser effect with sine or triangle modulation

  • reverb: a reverb effect (based on Freeverb) with several parameters for the room (like size and HF damping) as well as a possible predelay

  • tremolo: a tremolo effect with sine modulation using a double-sideband suppressed carrier modulation


The installation is as follows:

  1. Close the Reaper application or your DAW using ReaJS (if open).

  2. Make a subdirectory "Dr_TT" in either the "Effects" directory of the Reaper installation (typically in "\Program Files\Reaper\Effects") or - if your DAW uses some different directory for JSFX files - in that directory.

  3. Copy over all *.jsfx and *.jsfx-inc files from the distribution into this directory. If helpful, also add the documentation from the root directory.

  4. Restart Reaper (or your other DAW). You should now be able to select the plugins from the JSFX folder (they are all prefixed with "SoX").

Alternatively - and much easier! - you can use the ReaPack plugin and do an automatic install via the index.xml file in this repository.

After the installation via ReaPack all the effects can be found in the effects list of the Reaper installation.

Testing the Plugins

If you want to run the test, you also have to have a SoX installation. The test script "makeTestFiles.bat" in the Test directory assumes that SoX is available in the program search path.

The test script produces several sound and noise files and applies SoX audio effects to produces result audio files.

The Reaper project file "testSoxPlugins.rpp" references those test and result files and applies the corresponding effect plugins. Ideally (because the result files have inverted phase), everything should cancel out.


The detailed user manual can be found here.


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