Blue requires a Java 8 (also known as 1.8) or greater JVM (Java Virtual Machine) to be installed on your system, as well as Csound. Java installations usually come in two flavors: a JRE (Java Runtime Environment) which contains just a JVM for running applications, and a JDK (Java Development Kit) which contains the JVM as well as development tools. Because Blue comes with scripting tools that use JDK features, it is recommended to install the full JDK, and not just the JRE.

To test to see if you have a JVM installed and what version, at a command prompt type "java -version". If you see something along the lines of "command not found" then you need to install a Java Virtual Machine.

If you do not have Java installed, you can install the Oracle JDK available at:

On this page, look for the download link for Java SE and choose the JDK download for your platform. Be sure to choose the version of JDK that matches your CPU type and Csound version (choose 64-bit if in doubt).

Blue also works with OpenJDK versions of Java. These are pure open-source versions of Java that are often available through package managers on Linux. If you do use an OpenJDK version of Java, be sure to install JavaFX, a UI toolkit for Java that is often packaged separately from the main OpenJDK package. (Installing the Oracle JDK will include JavaFX automatically.)

Debian/Ubuntu Notes

If you are using Debian, Ubuntu, or a Linux distribution based upon one of those, be sure that you have JavaFX installed with Java. (If you hava Java installed but not JavaFX, you will find that Blue will open but an error happens during startup and a blank screen shows.) If you have OpenJDK Java installed, you can try running the command "sudo apt install openjfx" to install JavaFX and then try running Blue.

If that does not work, you should try installing Oracle Java. This can be done by using apt together with a PPA. Complete instructions are given here.