Melpomene's occasional description as mother of the Sirens connects to a fuller myth, recorded by the geographer Pausanias, of a singing contest between the Muses and the Sirens themselves, bird-bodied singers who rashly challenged the goddesses of song to a match with high stakes attached: whoever lost would surrender feathers from their wings to the winner. The Muses won, and, according to Pausanias, plucked the defeated Sirens' feathers to fashion crowns for themselves, an image that cast the Muses as active, even slightly vindictive competitors defending their own domain of song against presumptuous rivals, rather than as purely passive sources of inspiration waiting to be invoked by a poet. The story exists in variant forms with differing details about which Muse judged or presided, and ancient sources are not fully consistent about the Sirens' parentage either, some naming other Muses, including Melpomene, as their mother, which sits uneasily beside the same tradition making the Sirens the Muses' defeated rivals rather than their offspring.
The inconsistency is worth stating plainly rather than smoothed over: ancient mythographers evidently felt no strong need to reconcile a story in which the Sirens are the Muses' children with a separate story in which the Sirens are the Muses' rivals, and both circulated without either driving the other from the tradition. What the contest myth does add to Melpomene's own thin profile is a rare glimpse of the Muses acting collectively and competitively, defending the primacy of divine song against challengers with wings and voices of their own.