A hybrid piano can be created from an acoustic or a digital piano, but we need to be clear about our definitions of acoustic and digital. The essential difference between acoustic and digital pianos is in how each produces sound. In an acoustic piano, a sound is produced by the mechanical act of a hammer hitting strings, which causes the strings to vibrate. In a digital piano, the sound is produced electronically, either by playing a recording of a note previously digitally sampled (recorded) from an acoustic piano, or by physical modeling, in which a mathematical algorithm closely approximates the sound of that note on an acoustic piano. (Here we’re speaking only of that aspect of a digital piano that is designed to produce a piano-like sound. Digitals typically also can produce the sounds of many other instruments and non-instruments.)

Acoustic-based Hybrids: the MIDI Controller

The first hybrid pianos were not new instruments, but modifications of already existing acoustic pianos. In 1982, with the advent of the Musical Instrument Digital Interface (MIDI), a computer language for electronic musical instruments, instruments from different makers could “speak” to one another. Soon after, various kinds of mechanical contacts were invented for placement under the keys to sense keystroke information such as note, key velocity, and duration, and convert it into MIDI data. This MIDI information was then routed to synthesizers, which turned the information into whatever instrumental sounds the attached synthesizer was programmed to produce. When one instrument is used to control another in this manner through the transmission of MIDI information, the first instrument is called a MIDI controller. At the beginning, however, the sound of the acoustic piano could not be turned off, though it could be muffled in vertical hybrids.

Early mechanical key contacts were subject to breakdown, or infiltration by dust, and their presence could sometimes be felt by sensitive players, which interfered with their playing. The more advanced key contacts or sensors used today involve touch films or optical sensors that are more reliable and accurate, and add no significant weight to the touch. In time, too, mechanisms were invented for shutting off the acoustic piano sound entirely, either by blocking the hammers from hitting the strings, or by tripping (escaping) the action’s train of force earlier than normal, so that the hammers lacked the velocity needed to reach the strings. Headphones would block out any remaining mechanical noise, leaving only the sounds of the electronic instrument.

Not surprisingly, most makers of these MIDI controller/acoustic hybrid systems have been manufacturers of electronic player-piano systems. The same MIDI sensor strip used under the keys of these systems for their Record feature (which allows players to record their own playing for later playback) can also transmit the MIDI information to a digital sound source: either an internal source that comes with the piano (a soundcard) or an external source, such as a synthesizer or a computer with appropriate software installed. All player-piano systems today allow, through MIDI control, for the accompaniment of the acoustic piano sound by digitally produced sound, be they other piano-like sounds, other instrumental sounds, or even entire orchestras.

In addition to the accompaniment function, it turns out that these hybrid systems in which the acoustic piano can be silenced potentially have another very practical function. If your playing is likely to meet with objections from neighbors or family, being able to silence the piano and then play as loudly as you want, while listening through headphones, can be very handy. Realizing this, the major player-piano manufacturers make the MIDI controller feature available—without the player piano—relatively inexpensively. These MIDI controllers include a MIDI sensor strip under the keys, or optical sensors for keys and hammers, but no hardware and electronics that would make the piano keys move on their own. Usually, these systems come with a stop rail or other mechanical device to prevent the hammers from hitting the strings, as well as an internal digital sound source and headphones. When you move a lever to stop the acoustic piano sound, you turn on the digital sound source, which is heard through the headphones. Yamaha calls their version of this instrument Silent Piano; a variant whose digital piano sound is broadcast by the acoustic piano’s soundboard is called TransAcoustic. Kawai calls their hybrid piano series—including one model with a soundboard speaker system—AnyTime. PianoDisc calls their two add-on systems QuietTime and ProRecord; QRS’s version is SilentPNO.

But the accompaniment and “silent” functions of a hybrid MIDI controller/acoustic piano are only the beginning of what it can do. Just as the MIDI signal can be sent to a synthesizer or soundcard, it can also be sent to a personal computer or transmitted over the Internet. Regardless of whether a MIDI controller originates in an acoustic or a digital piano, it enables the instrument to interact with music software to record, produce notation, control instrumental voices on a personal computer, or interact with other pianos in the same room or on different continents. The potential for hybrids in creating and teaching music is limited only by the imagination of the user. Notation softwares—e.g., MakeMusic’s Finale, Avid’s Sibelius, and GenieSoft’s Overture—allow the hybrid piano’s keystrokes to be converted to music notation. This notation can be edited, transposed, split into parts for different instruments, played back, and printed out. The possibilities for teaching are perhaps even more powerful. Taking a lesson from a teacher in a different state, or a master class from a performer in a different country, becomes feasible with hybrid technology, particularly when combined with the player-piano features. Exacting copies of performances can be sent to similarly equipped instruments for playback, and critiques—with musical examples—can be sent back to the student. Some systems enable this interaction in real time over broadband connections, complete with synchronized video.

As we’ve said, most of the activity in the field of acoustic hybrids has been among player-piano makers, whose offerings have been either specialized (Silent Piano) or add-ons (QuietTime, SilentPNO). However, MIDI capabilities are now standard in all acoustic pianos, vertical and grand, made by Story & Clark, a subsidiary of QRS, the only piano maker so far to have done this. If you add a stop rail to silence the piano (available from QRS) and a sound source, you could turn one of these instruments into a “silent” hybrid like those described above. But even without those additions, a Story & Clark piano can be used with a personal computer and music software for recording, notation, controlling computer-produced instrumental voices, or any of the myriad other uses possible with a MIDI controller.

Digital-based Hybrids: Replicating the Acoustic Experience

Now, you may wonder: If you’re going to use a piano to interact with a computer, play piano sounds silently, or make the sounds of other instruments, why bother with an acoustic piano at all? Why not just use a digital piano or keyboard of some kind? The reason: the experience. Digital pianos are long on functionality but short on, so to speak, atmosphere. For those used to the looks, touch, tone, or other, less tangible aspects of acoustic pianos, digital pianos, in their “pure” form, just don’t cut it—so digital piano makers have spent a great deal of time, energy, and money trying to mimic one or more of these aspects of acoustic pianos. The closer they get to duplicating the experience of playing an acoustic piano, the more they earn the right to the designation hybrid—because, when you get down to it, the purpose of playing an acoustic piano is the experience.

The first aspect of acoustic pianos that digital piano makers mimicked was, of course, their looks—indeed, a large segment of the digital piano market consists of acoustic-piano look-alikes. But that alone isn’t enough to earn the label hybrid. Next, the action mechanism of the acoustic piano found its way into the digital piano. Much engineering has gone into the numerous action designs in digitals, always in the attempt to make their feel and response as close as possible to those of a “real” piano. Many digital piano actions these days have weighted and/or wooden keys with ivory-like keytops, and other enhancements that do a reasonable job of emulating an acoustic piano action; still, advanced pianists, especially players of classical music, are unlikely to be completely satisfied by most of these.

Some digital-piano models now use real or only slightly modified acoustic-piano actions to trigger the piano’s sensors (the hammers are small and don’t actually strike strings). With such an action, there’s no need to simulate certain action processes, such as escapement, because, mechanically, those processes are what is actually occurring. The first instrument to be formally named a Hybrid Piano was Yamaha’s AvantGrand series, unveiled in 2009. The AvantGrand elevated the digital piano to a new level with a number of hybrid technologies, first of which was a real piano action. All three AvantGrand models have grand-piano actions, but whereas the model N3X is also shaped like a grand, the cabinets of the lower-cost N1 and N2 are closer to that of a vertical piano (which brings up the interesting observation that whether to call a digital piano a “grand” or a “vertical” is not a simple decision). In 2012, Yamaha introduced the model NU1 Hybrid Piano, the first digital piano with a real vertical-piano action.

To emulate the feel of an acoustic-piano action, it’s necessary to also address the feel of the dampers and pedals. When you depress the sustain pedal on most digital pianos, you’re pressing a spring with constant tension. This is not how the sustain pedal feels on most acoustic pianos, in which the initial movement meets little resistance as the pedal takes up a bit of slack in the mechanism that lifts the dampers. Once the mechanism begins to actually lift the dampers, the resistance increases. Here again, the AvantGrand does a convincing job of conveying the feel and, perhaps more important, provides the degree of control available with an acoustic’s sustain pedal, including half-pedaling and incremental control. Kawai’s Novus NV10 Hybrid digital piano, which also uses an acoustic-piano action, goes a step further: Just as on an acoustic piano, the Novus’s touch weight varies based on whether or not the sustain pedal is depressed.

One aspect of the traditional acoustic-vs.-digital argument that changes with the addition of a real piano action is the digital’s advantage of rarely needing maintenance. While the AvantGrand, NU1, and Novus models will never need to be tuned, eventually their actions will require some degree of adjustment or regulation. (We’ll bet the piano technician will be surprised when, on arriving to regulate an action, he or she finds that the “piano” is a digital.)

Of course, makers of digital pianos have put more effort into copying the tone of the acoustic piano than any other aspect. How they’ve done this is beyond the scope of this article, but an interesting technique used in some models (e.g., the Kawai CS11 and CA-98) is to add to the digital an acoustic-piano soundboard, set in motion by transducers, to augment the piano’s conventional speakers and give the instrument a more natural tone. Others are the installation of elaborate speaker systems, and the use of sampled concert grands. An example is the N3X’s four-channel sample set and 12-speaker audio system, which easily trick the ears into thinking that considerably more than four feet of piano are in front of you. The Avant Grand and NU1 models all use samples from Yamaha concert grands for their sounds; the Novus uses samples from a Shigeru Kawai concert grand.

But there’s even more to copying the acoustic-piano experience than its looks, action, and tone, and this brings us to aspects that are more difficult to precisely quantify or describe. With the AvantGrand, one of these—the vibrations generated by the strings and transmitted throughout the instrument—has been duplicated. Yamaha has added this ingredient to the N2 and N3X by connecting transducers to the action to send the appropriate frequency and degree of vibration to the player’s fingers through the keys. This is where the experience of playing becomes a bit spooky. Not unlike an amusement-park ride that convinces your brain that you’re dodging asteroids while hurtling through space when you are, in fact, fairly stationary, the AvantGrand’s Tactile Response System quickly convinces you that you’re feeling the vibrations of nonexistent strings.

One area in which digital pianos are not intended to emulate acoustic instruments is that of price. Most hybrid pianos that can provide the sound of and, in some cases, the experience of playing a concert grand, are priced similarly to a company’s least expensive acoustic grands and verticals. Actually, such comparisons are barely possible—the acoustics lack many of the digitals’ features, such as onboard recording, USB memory, transposition, and alternate tunings.

Which Side Are You On?

As the market for hybrid pianos grows, buyers will increasingly have to choose between acoustic pianos with digital enhancements and digital pianos that try to re-create the acoustic experience. Decisions will be made by weighing the relative quality, and importance to the buyer, of action, tone, looks, and features, as well as price. More advanced classical pianists whose digital needs are modest, and buyers who, among other things, are looking to fill a living room with a large, impressive piece of furniture, will probably tend to stick with the acoustic-based hybrid, at least for now. Those whose musical needs are more general, or who have a strong interest in digital features, may find digital-based hybrids more cost-effective.

Another factor that may come into play is that of life expectancy. A good acoustic piano will typically function well for 40 or 50 years, if not longer. Few digital pianos made 15 to 20 years ago are still in use, due either to technological obsolescence or to wear. True, the relevant technologies have evolved, as has the design of digital pianos and the quality of their construction. However, if past experience is any guide, pianos that are largely acoustic but include digital enhancement may well last for many decades; digital pianos enhanced with acoustic-like features are unlikely to last as long.

The piano has evolved a great deal since Bartolomeo Cristofori invented it in 1700, and that evolution continues. Today it’s possible to buy a piano with an ABS-Carbon action (Kawai), a carbon-fiber soundboard (Steingraeber Phoenix), or one that looks as if it was made for the Starship Enterprise. The hybrid piano’s blending of acoustic and digital technologies is just another step—or branch—in that evolution.