Piano Resurrection

Recordings of past piano masters are a vital musical resource, but they can be difficult to listen to with modern ears that are accustomed to high-quality
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Recordings of past piano masters are a vital musical resource, but they can be difficult to listen to with modern ears that are accustomed to high-quality audio reproduction. What if there were a way to re-create these classic cuts using modern instruments and recording techniques? A company called Zenph Studios (www.zenph.com) has developed a process whereby any solo-piano recording can be completely re-created, with every note and nuance faithfully reproduced.

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FIG. 1: Zenph Studios built a recital hall around a 9-foot Yamaha Disklavier Pro (left) to help in the development of its software. Also on hand is a Steinway Model D.

The Zenph process is made possible by Yamaha's Disklavier Pro, a souped-up version of the company's MIDI-driven player piano. What makes the Pro so special is Yamaha's enhanced implementation of MIDI, which is formally called XP (eXtended Precision) Mode, and informally known as high-resolution or high-definition MIDI.

For example, instead of representing Note On and Note Off Velocity with 7 bits, XP Mode uses 10 bits. It also uses 10 bits to represent each hammer's movement, and 7 or 8 bits (depending on the specific Disklavier Pro model) to encode each pedal's position. The extra bits come from undefined Control Change messages, allowing the Pro's internal sequencer to capture much more of the player's articulation and nuance than conventional MIDI can.

The folks at Zenph Studios realized that XP Mode on a Disklavier Pro could be used to “reperform” classic piano tracks if those recordings could be accurately transcribed and converted into high-resolution MIDI data. Audio-to-MIDI systems have been around for years, but they are not completely accurate (especially with complex polyphonic input), and they can only encode the performance with conventional MIDI messages, which can't capture the nuances of world-class artists.

Unfortunately, Zenph found that conventional sequencers don't know what to do with high-res MIDI data, often garbling or discarding the extra bytes. In addition, Yamaha does not publish the XP Mode spec, so Zenph had to reverse-engineer it in order to write sequencing and editing software. To aid in that effort, the company built a temperature- and humidity-controlled recital hall around a Disklavier Pro (see Fig. 1), and recorded various pianists with its internal sequencer to study how humans actually play.

The company also created software that converts acoustic-piano recordings into WAV files and transcribes them into high-res MIDI data. The process requires human interaction to achieve a successful result. And it doesn't happen in real time; the first three-minute demo took two weeks of human and processor time, though Zenph expects to reduce that time factor as the system is refined.

Once the data is compiled, it is used to drive the Disklavier Pro, the acoustic sound of which can be recorded with modern equipment and techniques. The first demonstrations include Glenn Gould's 1955 recording of Bach's Goldberg Variations and tracks from Art Tatum and Alfred Cortot, a French pianist recorded in 1926. The new recordings were done by famed engineer Peter McGrath in 5.1-channel surround sound using a DSD (Direct Stream Digital) recorder, the format used for SACD. The end result is remarkably effective; listening on headphones to the original recording in one ear and the re-created recording in the other ear makes it easy to hear if anything is amiss, down to the smallest detail.

Zenph has no plans to release its software; instead, the company intends to provide a service to record labels who want to revitalize their archived piano recordings. The only things omitted from the new recordings are all the flaws of those early tracks — noise, clicks, pops, out-of-tune instruments, poor dynamic range and frequency response — leaving the artistry completely intact. I will miss Gould and Erroll Garner muttering as they play, but that's a small price to pay for such a dramatic improvement in the quality of these classic recordings.