PROTARCHUS: Very true.
SOCRATES: And yet not by knowing either that sound is one or that sound is infinite are we perfect in the art of speech, but the knowledge of the number and nature of sounds is what makes a man a grammarian.
PROTARCHUS: Very true.
SOCRATES: And the knowledge which makes a man a musician is of the same kind.
PROTARCHUS: How so?
SOCRATES: Sound is one in music as well as in grammar?
PROTARCHUS: Certainly.
SOCRATES: And there is a higher note and a lower note, and a note of equal pitch:—may we affirm so much?
PROTARCHUS: Yes.
SOCRATES: But you would not be a real musician if this was all that you knew; though if you did not know this you would know almost nothing of music.