Pitch modulation refers to the variation in the pitch of a sound over time. This can occur naturally in music, where a singer or instrument may slightly change pitch to create a more expressive performance. It can also be achieved electronically through various effects and synthesizers, allowing for creative sound design. In the context of audio processing, pitch modulation can be used to create vibrato or other effects that enhance the listening experience. Techniques such as frequency modulation and amplitude modulation can alter the pitch, adding depth and complexity to sounds in genres ranging from classical to electronic music.