-- groups progressions in a CPD by artist, denoting the artist with a string
getByArtist :: ChordProgressionDatabase -> [(String, [TimedChordProgression])]
getByArtist cpd = (getProgressionsCategorizedByCriterion cpd "Artist")
getByArtist :: ChordProgressionDatabase -> [(String, [TimedChordProgression])]
getByArtist cpd = (getProgressionsCategorizedByCriterion cpd "Artist")
getByArtist cpd = (getProgressionsCategorizedByCriterion cpd "Artist")