 Crosstalk or "leakage" occurs when the instrument's magnetic pickups receive the signal from rotating metal tonewheels other than those selected by the organist.Hammond considered crosstalk a defect that required correcting, and in 1963 introduced a new level of resistor–capacitor filtering to greatly reduce this crosstalk, along with 50–60 Hz mains hum.However, the sound of tonewheel crosstalk is now considered part of the signature of the Hammond organ, to the extent that modern digital clones explicitly emulate it.