I’ve come to the discovery that I can help reduce the large amount of duplications by extracting ISRC’s from my CD’s and adding them.
However I just want to clarify something, reading on the Wikipedia article it mentions:
ISO 3901 was completed in 1986. In 1988, the IFPI recommended that its member companies adopt ISRCs for music videos. In 1989, the ISO designated the IFPI as the registration authority for ISRCs. The IFPI, in turn, delegated part of the administration of ISRCs to several dozen national agencies, which allocate ISRCs to both record companies and individuals. The national agencies began assigning ISRCs for music videos in August 1989.
The Japanese recording industry began encoding ISRCs on audio CDs in November 1989. The IFPI and the Recording Industry Association of America (RIAA) then developed detailed recommendations for this practice, and for ISRC assignment in general. The IFPI adopted the recommendations in March 1991 and they went into effect for IFPI members on 1 January 1992.
So would this mean that any CD produced before 1/1/1992 likely does not have the ISRC’s encoded? I’ve found a few compilations that I have from 1991 and 1990 (for example) have this information missing.