The formant region of an instrument is the frequency region which is emphasized relative to other harmonics and determines the unique sound of an instrument. A vibrato is produced by periodic changes in the pitch of a musical tone. A tremolo is produced by periodic changes in the amplitude of a musical tone. A chorus effect occurs if many instruments play the same part in unison. The sound quality is quite different from the individual instruments due to superposition of many similar tones with slightly different frequencies and tone qualities.
All instruments have primary resonators and secondary resonators and often resonating cavities.