The figure of the siren serves as a metaphor for human singing and musical femininity in a number of texts ranging from the sixth to the fourteenth centuries. Bird comparisons in general allowed medieval writers to signal a mismatch between positive musical features (attractive song, singer, and sound) and negative ethical features (the sin of sweetness as a form of gluttony or lechery), a dichotomy that seems to have been felt acutely in the later Middle Ages. References in John of Salisbury's Policraticus, bestiaries, music theory, and lyrics are brought to bear on the overlap between the figures of the siren and the fowler, both of which lure aurally. Arnulf of St-Ghislain's striking use of a siren comparison can be informed by the range of meanings for the siren in the Middle Ages and his borrowing of bird and animal comparisons from Alan of Lille's De planctu Naturae. Bird-like features of both listener and singer in medieval accounts of musical hearing add to this picture of aural danger.