Also, note that CMD is not meant to RUN commands to create your image. Instead, it’s used to start the container. That may very well be what you want, but that’s not clear to me. Many images define an entrypoint for that (for which CMD then defines the default arguments). But true, CMD can be used too. Be sure to read its documentation to determine if you indeed want to use “the shell form” for your downloaded thing:
If you use the shell form of the CMD, then the <command> will execute in /bin/sh -c
I had a similar issue with alpine. It turned out the error message was not “talking about” the executable but the libraries it used. Are you sure playit compatible with alpine? Have you tried it with a debian based system (or any other)?