About the beta
The beta version is available to all RapidComposer owners, so this is not a public beta. The beta version is usually solid for serious work, but there may be smaller bugs in new functionality. It includes the latest bug fixes, and new features, sometimes months ahead of the release.
Download
The download URL has changed since v3! You need to add the word "beta" to the download URL. E.g. the URL xyz.php becomes xyzbeta.php.
I will gladly send the URL to any RapidComposer owners by request (PM or e-mail).
Installation
Execute the installer. This new version uses the Documents/RapidComposerV4 folder. The program imports your v3 settings if it can locate the Documents/RapidComposerV3 folder. Please note the custom phrases and rhythms folder will point to your existing folders in Documents/RapidComposerV3.
Updates
The beta RSS feed (beta.xml file) is not used anymore. Instead, a new topic will be created with the beta history.

v4.0 is the biggest development in the history of RapidComposer. Both the internals and the user interface have been reworked. As a result new features will be added more quickly in the future, with less bugs or stability issues.
The plug-ins have been rewritten from scratch, and became self-contained, which means bridging to the main application is not needed anymore (which proved to be fragile in some cases).
Binary compatibility with v3 composition files ended. Phrases saved in v3 can be loaded, except for phrase generator presets, and phrases in text format. This means almost all contributed phrases are usable, except for about 340 of 42000+.