The Daily Mixes could have a slider control to select how much novelty you want in your mix. If the slider is totally to the left then it plays only tracks you have listened to before. If you put the slider totally to the right then it plays only tracks that you have never listened to before. The positions in the middle would be different combinations of these two extremes.
Sometimes I just want to listen to recommendations in a given genre without having to go through all my old tracks that I could easily make into a playlist anyway.
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