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WebSid (WebAudio version of Tiny'R'Sid)

This is a JavaScript/WebAudio based C64 emulator / music player. This plugin is designed to work with version 1.02 of my generic WebAudio ScriptProcessor music player (see separate project).

It allows to play .mus and RSID/PSID format *.sid music files. (Respective music files can be found here:

There also is a WordPress plugin that allows to easily integrate the player:

This current version uses a cycle-by-cycle emulation approach (i.e. it has been substantially rewritten). As compared to the previously used "predictive" approach it allows for a much simpler implementation and it simply avoids most of the problems that had haunted the old implementation (e.g. correct timing of ADSR-delay bug, etc). Unfortunately the new implementation is computationally much more expensive (50-100% more CPU).

The emulator logic is written in C/C++. This code is then cross-compiled into a JavaScript library suitable for the Web.

Known limitations: see src/KnownLimitations.txt for details

alt text

An online demo of the emulator can be accessed using: or


  • old/original TinySid PSID emulator code (there is not much left of it..) - Copyright (C) 1999-2012 T. Hinrichs, R. Sinsch
  • "combined waveform" generation, "waveform anti-aliasing" and "filter" implementation by Hermit (see
  • based on various reverse engineering information by: Christian Bauer, Wolfgang Lorenz, resid team, etc
  • playback of Compute! .mus files is based on "Enhanced Sidplayer" by Craig Chamberlain

Howto build

You'll need Emscripten; see . In case you want to compile to WebAssembly (see respective "WASM" switch in the make-scripts) then you'll need at least emscripten 1.37.29 (for use of WASM you'll then also need a recent version of my respective "WebAudio ScriptProcessor music player").

The below instructions assume a command prompt has been opened within the "websid" folder, and that the Emscripten environment vars have been set (run emsdk_env.bat).

Running the makeEmscripten.bat will generate a JavaScript 'Tiny'R'Sid' library (backend_tinyrsid.js - and a separate tinyrsid.wasm file if you are compiling to WebAssembly) including necessary interface APIs. This output is directly written into the web-page example in the "htdocs" sub-folder. (This generated lib is used from some manually written JavaScript/WebAudio code, see htdocs/stdlib/scriptprocessor_player.min.js). Study the example in "htdocs" for how the player is used.

Running the makeEmscriptenTest.bat will generate test version which is directly written into the web-page example in the "htdocs_test" sub-folder (the respective page then allows to run the various tests from Wolfgang Lorenz's "test-suite").

Disclaimer: the .sh version of the make-script has been contributed by somebody else and I am not maintaing it or verifying that it still works.

Note: Due to some bug in Apple's JavaScriptCore (as of iOS 11.4) the regularily built version will not work on iOS devices. As a workaround you can compile using "-s SAFE_HEAP=1". This will make for slower code but it seems to be the only way around the iCrap bug.


The current version requires version 1.02 (older versions will not support WebAssembly) of my (use of the most recent version is recommended).


Terms of Use: This software is licensed under a CC BY-NC-SA (

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