It’s not the spectrograms, it’s all the other stuff about albums (whether local or TIDAL) that are held in the Roon database with their cross-linkages…
In RAM, we create hundreds of database indexes for the various types of metadata we hold, and cross references as well. One example of what this enables is that we can highlight artists in a bio/review that only exist in your own library.
For the content itself, it’s spread out and quite a bit larger than you’d expect. The typical compilation album has thousands of credits associated with it.
If you run on an SSD, you get a 10x-100x performance for jumping around the databases on disk (since …