Bach's Goldberg Variation #6 - Canon at the second.

This is the 6th Goldberg variation. The second voice comes in one bar after the first voice and is the 2nd note you hear in the upper register. The theme of the variation: G, F#, E, D, B, C, D, G, is difficult to hear clearly in this variation.
Every third variation is a canon, each consecutive one has the second voice starting a note higher.
canon at unison, at the second, at the third, etc.