The quality of a note, also known as timbre, depends on its overtones. Overtones are the additional frequencies produced by an object when it vibrates. While the fundamental frequency of a note determines its pitch, it is the presence and relative strength of overtones that give the note its distinctive timbre. Different instruments or voices playing or singing the same note will sound different because of the unique combination of overtones they produce. Amplitude refers to the loudness of a sound, while frequency is the number of vibrations per second and determines the pitch of the sound.