Visual indicator of track similarity

When you have a track playing on a deck, it's good to be able to quickly find other tracks that have similar beats and keys, so you can load them up ready to play, and spend more time focussing on other stuff. At the moment, the only way to do that is to read the BPM/key columns for each track, and find what you want. I have a terrible memory of the circle of fifths, so key matching is not trivial.

It would be *really* handy to have some visual indicator of the similarity of each track to the currently playing track (the sync master). This could be as simple as having a "LED" indicator light (in a new column) that gets brighter when a track is more similar. This would give you a *really* quick way to scan through a library/crate and pick out suitable tracks.

Similarity would be based on weighted key similarity and BPM similarity, ideally where there is an option in the preferences for the user to set their weight preferences. It could also include things like genre, year, etc.

Another option for the UI might be to just colour the background of the track row in the library/crate. Also, if each deck is coloured, it might be possible to have more than one indicator per track that match the colour of the track in each deck.