Sudden duplicates after starting Music subscription

Before starting my Music subscription, I had a few thousand songs in my library ( based on my iMac running latest version of Catalina OS) - some purchased and downloaded from iTunes, and some uploaded from my private CD collection. I subscribed to Music just yesterday and suddenly I find hundreds of duplicate songs across my iOS devices! Does anyone know how I can stop this from happening and remove all the true duplicates in an effective way? Very annoying!