A well-known recording company recently released a new recording of Glenn Gould performing the Goldberg Variations. The recording date was summer 2006. Curious, not? Another pianist with the same name as the legendary Canadian musician?
Actually, the recording was made using measurements of the original, old recordings that were used to remake the performance on a computer-controlled grand piano, a modern pianola. In the recording studio a grand piano was moving its keys without someone behind the piano. Glenn Goulds original performance was re-performed on a modern instrument in a modern studio.
The technology that was used dates from the early nineties, a time when several piano companies (including Yamaha and Bosendorfer) combined MIDI (an industry standard for communicating between computers and electronic keyboard instruments) and modern solenoid technology with the older idea of a pianola. Old paper piano rolls with recordings of Rachmaninoff, Ravel, Stravinsky and others were translated to MIDI and could be reproduced 'live' on modern instruments like the Yamaha Disklavier. Until now, the only left challenge was to be able to do this for recordings of which no piano-rolls exist.
Besides the technicalties of all this, for most people the real surprise -- or perhaps disillusion -- might well be the realization that a piano performance can actually be reduced to the 'when', 'what' and 'how fast' the piano keys are pressed. Three numbers per note can fully capture a piano performance, and together with the pedaling information it allows for replicating any performance on a grand piano(-la). The moment a pianist hits the key with a certain velocity, the hammer releases, and any gesture that is made after that can be considered merely dramatic: it will have no effect on the sound. This realization puts all theories about the magic of piano touché in a different perspective.
Nevertheless, while it is relatively easy to make the translation from audio (say a recording from Glenn Gould from 1955) to the 'what' (which notes), and the 'when' (timing) in a MIDI-like representation, the problem is in the 'reverse engineering' of key velocity. What was the speed of Gould's finger presses on the specific piano he used? The Zenph Studios claim to have solved it for at least a few recordings. Only trust your ears.