While I also think this would be extremely useful for cases such as the ones described (being more easy to identify stand out tracks, or for example if you're only interested in 2 or 3 certain game arrangements in a more varied dojin album), it could be really hard to implement (talking from ignorance here) and it would make "gaps" pop out. What about albums which don't have specific track-composer credits (capcom comes to mind) or even worse, missing composer credits altogether?
And there's the "workload" factor in some albums... imagine rating every single song in the Outrun box :P.
There should be an intermediate solution like what SecretSquirrel suggested. Whatever the case, I'm looking forward to any improvement in this regard you might decide to take on.
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