French composer Claude Debussy said "Music is the space between the notes." Mr. Debussy might have meant the silence between the notes, or he might have meant the difference in frequency between the two pitches. Musician, Peter Kagstrom, and Singer, Kristi Deprin, talk about intervals, or the relationship of two different notes in this episode. Learning the relationship between two notes can help in ear training and grow relative pitch. Some notes in sequence sound good, or harmonious, and some sound not as pleasing, or dissonant. Thinking about harmony and dissonance, Peter and Kristi explore songs in the key of D, the happiest of keys, and conclude the episode with the children's classic, "Itsy Bitsy Spider."