Chorus Ex Machina is an open source, physically modelled chorus synthesizer. It can sing realistic sounding text in a variety of languages. Here is an example of music created with it, so you can hear what it sounds like.
The sound produced by Chorus Ex Machina is completely dry. It models only the singers, not the room they are in. To get a realistic sound, it is essential that you add an appropriate reverb.
Chorus Ex Machina can be used as a VST3, CLAP, or AUv2 plugin. The Releases page has compiled versions for Windows, Linux, and macOS. If instead you want to build it from source, first install the Rust compiler. To build the VST3 and CLAP plugins, execute the following command from this directory.
cargo xtask bundle chorus_ex_machina --release
To build the AUv2 plugin, first build the CLAP plugin then follow the instructions in
the au subdirectory.
On macOS, you may find it is necessary to compile the plugin yourself. By default, Apple blocks all programs from running unless they are digitally signed by a developer who pays $99/year for an account, which I choose not to do. There are workarounds which can allow the precompiled versions to work, but those workarounds have gotten steadily more difficult with time. Compiling it yourself avoids this problem.
For instructions on how to use the plugin, see the documentation, which is also available in the plugin's user interface.
Some DAWs intercept some or all keystrokes and interpret them as commands to the DAW itself rather than sending them to the plugin's editor. This interferes with typing text into the Chorus Ex Machina editor window. There are workarounds to address this problem.
Reaper: In the FX window, click the "+" button at the top of the window. Select "Send all keyboard input to plug-in".
Ableton: Create a text file called Options.txt and place it in the Preferences
directory. It should contain the line
-_EnsureKeyMessagesForPlugins
See the Ableton Knowledge Base for more details.