History: An expressive feature of subtractive synthesis is...

An expressive feature of subtractive synthesis is...

• the filtering properties -- pitch, volume, and space -- can vary over time.
  Pitch is a perceptual characteristics, not a physical property.
• the subtractive properties -- pitch, volume, and space -- can vary over time.
  There is no such thing as 'subtractive properties'.
• the subtractive properties -- frequency, amplitude, and phase -- can vary over time.
  There is no such thing as 'subtractive properties'.
• the filtering properties -- frequency, amplitude, and phase -- can vary over time.
  Good job!