Hey meburgo4,
Thanks for clarifying that for us.
You can play music from a CD connected to an external drive in on your Mac per the article, Play CDs in Music on Mac. However, you may need to manually select your Bluetooth speakers in the AirPlay pop-up menu at the top of the Music window, and the volume control on the speakers isn’t turned down after you start playing the CD.
Still not working? The coding and technology changes when you import or download content from a CD to Music on your Mac. Songs available from Apple Music, the iTunes Store, or imported and downloaded to your library uses an encoder to convert the song to the most compatible file format for Apple devices. You can lear more about this concept in the Apple Music User Guide article, If you have problems playing music on Mac.
This may also be why the music is playing to your Bluetooth speakers without issue when you download it.
Kindest Regards.