In the case of many of these variations, he didn't tell you the tempo. So it's very difficult to decide how to play this music. I had to do a lot of study and analysis of this score in order for myself to come to terms with it. Bach made a world that had never existed before. One of its aspects is that it's very cohesive.
Every note is dependent on the next note, and it makes an organic whole.
This inevitability and, at the same time, surprise of every note is, I think, a miracle. Part of Perahia's study of the Goldberg Variations included practicing the work on a harpsichord, since it was written to be performed on a double-manual harpsichord. He wanted to better understand the technical ways in which the variations emerge through rhythm, articulation, rubato and other qualities, which are achieved in different ways on the piano. He explains his decision to play the work on a modern piano by citing the instrument's ability to bring out the extraordinary structure of the Goldberg Variations . It's a living, breathing emotional experience.