A three-dimensional diagram of the 400 most recorded operas in the catalog. Operas that share singers or conductors are drawn near each other, and where a composer's operas gather, an outline is drawn round them and labelled. It is driven by a pointing device and has no keyboard equivalent. The same relationships are available as text: Six Degrees traces the chain of shared recordings between any two singers, and every record’s own page lists the cast of each of its recordings.