History: What does the number of voices do?

What does the number of voices do?

• The number of voices determines how many sounds the instrument can modify at the same time.
  Usually refers to create.
• The number of voices determines how many pitches the instrument can modify at the same time.
  Usually refers to create.
• The number of voices determines how many sounds the instrument can create at the same time.
  Correct!
• The number of voices determines how many pitches the instrument can create at the same time.
  You can create more than one of the same pitch.