Rating music is a way of sorting and grading your music, but on its own has little purpose. You probably know if a track is one you love without needing to give it 5 stars. The exception is probably where you have multiple versions of the same song – rating helps to identify the best version unless you have a mind like a filing cabinet. However, in combination with auto playlists rating becomes essential. Instead of creating manual playlists that have to be manually updated, you can create a playlist (say Best of Pink Floyd) and give it a rule that it is to contain tracks by Artist=Pink Floyd and Rating >= 3 stars. Thereafter, any Pink Floyd track given 3 stars or more will appear in this playlist.
Ratings also give you the opportunity to create auto playlists like the iTiunes My Top Rated that contains any track with 4 stars or more.
Ratings are of course very personal, and very subjective. The “rules” for if a track is a given rating will vary by individual, and deciding to grade a large collection is daunting. I started grading when I started using iTunes and then as I added new tracks it was easy to grade them after first listen. There are tools for various music apps (iRate for iTunes) that use an algorithm to rate tracks based on time in your collection and number of times played.
Whatever personal criteria you use I think the key things are that it is “quick and dirty” – it shouldn’t need much consideration, and perhaps your emotional response can be guide in terms of how much do you want to listen to that song again? The system should not be absolute – I personally see no problem with rating a track 4 star and then at a later date when it no longer floats your boat demoting it to 2 star. You didn’t get it wrong, the re-rate can be due to all sorts of reasons.
It is I think important to think that no rating is fixed in order that you don’t spend time agonising over if it is 3 star or 4 star. Some songs I have rated after 10 seconds of listening based on my emotional response, not analysis. However, everyone is different.
So I use a 5 level system in which every track is graded from 1 to 4 stars. These then feed auto playlists such as “All Very Good” which is every track rated 3 stars or more. I have however found that in reality I can only grade a song into 4 categories as in my system there is Good (2*), Very Good (3*), Excellent (4*) and Loved (5*). Personally finer grading is difficult without deeper analysis and the whole point is to listen to the music.
For me grading is a way to access music, not an end in itself. Others may disagree. So what about 1 star, what gets that?
I use 1 star for tracks I am not sure about. I like them enough to have in my collection, but they perhaps need more listening to before rating higher. It is also a repository for demoted music that I have decided I don’t particularly like but am not ready to delete yet. I have an auto playlist for 1 star tracks that I have named “Twilight Zone”, a zone between deletion and a permanent place in my collection.