MUSIC THEORY – Beats and Just Noticeable Difference In this music theory animated tutorial made by Walk That Bass, you are going to learn what BEATS are and understand what the concept of Just Noticeable Difference is. When you play two notes a wide interval apart on the piano – like a 5th, you hear two distinct pitches. But if you play two notes really close to each other – having a frequency of less than about 30 Hz between them, like a semitone – then we don’t hear two distinct pitches. Inste