CalmusComposer 4.6 for Mac was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. We recommend checking the downloaded files with any free antivirus. The program lies within Audio & Video Tools, more precisely Music Production.
From the developer:
CalmusComposer is an innovative tool for musical composition - even in real time. It composes music from the input created by the user, or generates music by itself by using the internal library. It is a complex composing system with simple interface. A new option for composers or anyone wanting to become a composer.
You may want to check out more software for Mac, such as SmartMusic Studio, Speak or SH-201 Librarian, which might be related to CalmusComposer.