Melody, after listening to the Sonata of Darkness, acquired extra-sensitive hearing and uses this ability in many useful ways. She is able to track targets or hear conversations from hundreds of meters away. Melody can even differentiate one's footsteps from another, enabling her to determine the number of people in a crowd whilst picking out the sound of her target's footsteps, for example, in a city. She can hear the other's heartbeats and tell their emotional states as a result; or fluctuations to tell whether they are lying or not. Her hearing also enables her to ascertain the skills of others from the sounds they make, such as knowing that Killua is a former assassin from his steps.
Welfin can hear conversations transmitted on the frequency of a normal mobile phone.