Physical Modeling vs. PCM Synthesis

Unlike many of the stage pianos it competes with, the Physis H1 uses a technique called physical modeling to synthesize many of its sounds. Physical modeling is a method of creating sound in which the vibrations made by a musical instrument are described by a mathematical algorithm. In the case of a piano, the algorithm describes, among other things, the motion of a vibrating string, and can take into account factors such as the thickness of the string, the mass of the hammer striking it, and the resonance of the soundboard — and, literally, hundreds of other factors. By changing the values of these parameters, the sound can theoretically be changed to model almost any acoustic instrument, and can even be pushed past the point of what's physically possible in the real world. Physical modeling also offers the advantage of being able to more easily take into account real-world phenomena such as the sympathetic resonance of other strings that occurs when the damper pedal is depressed, and the subtle yet easily perceptible change of timbre that occurs when a note is struck with greater velocity.

Most of Physis's competitors use PCM, or sample-playback, synthesis. (A prominent exception is the Roland V-Piano, which uses physical modeling.) PCM synthesis involves making recordings of each note of an acoustic piano in a recording studio. These recordings, or samples, are then stored in the memory of a digital piano. When the digital piano's keys are played, the recordings are played back. The challenge for PCM systems is that recording every note at its full duration at multiple velocities requires huge amounts of memory that are prohibitively expensive for most digital piano designs. Also, in PCM synthesis, each iteration of a particular note is exactly the same and sounds exactly the same as every other iteration of that note. In an instrument that uses physical modeling, on the other hand, repeated keystrokes produce slightly varied repetitions, which adds to the sense of realism. To be fair, many digital-piano makers who use PCM synthesis supplement their sampled sounds with synthesized effects, for a more realistic sound.

The Control Interface

The Physis H1 has a sleek, modern look, with brushed aluminum trim. Rather than the pushbuttons found on many digital pianos, the H1's control interface is a multi-touch glass panel, like that of a tablet computer. This design has the advantages of no moving parts that might fail over time, no holes punched in the top of the chassis that might allow debris to enter the unit, and makes cleaning the front panel as easy as wiping it with a soft cloth. The slight disadvantage is that, as with a tablet computer, interacting with it leaves visible fingerprints. I also found that there was a slight learning curve to successfully interacting with the touch panel. At first, it seemed as though the H1 wasn't registering all of my touches. After my first hour with it, however, I easily adapted to it, and its use became second nature.

The H1 sports a beautiful, high-resolution, 4.7" color display that's easy to read under just about any lighting conditions. When I began using the H1, it took just a moment to understand that while the piano would respond to my touch in many places on the touch panel, the main display wasn't one of them. According to the Physis website, this is a deliberate design decision, as the resulting fingerprints could obscure the user's view of the display. Instead, the main display is surrounded by four function icons, with which the user can directly select items on the display. There are also four cursor arrows and a virtual slider control, to select parameters on the display and modify their values. Dragging a finger over the slider coarsely adjusts the value of the selected parameter, while quick taps at either end of the slider increase or decrease the value in finer increments. The menus and screens are clearly laid out, easy to navigate and understand, and many offer online help. I was able to easily access and understand every function of the H1 without ever having to open the manual.

Action and Pedals

The H1's 88 hammers are graded into four weight zones. It's easy to globally adjust the H1's velocity-response curve so that players with heavier or lighter touches can easily find the response they're looking for. The instrument's wooden keys have what Physis calls "Ivory Feel" keytops — not perfectly smooth, like high-polish plastic keytops, but with a subtle texture similar to ivory's. Although I'm accustomed to smooth plastic keys on my keyboards and pianos, I didn't find the texture distracting or unpleasant. The key dip felt right, and the action was quick without being too light, too heavy, or sluggish. Rapid, virtuosic passages came out easily, and I was able to play for more than an hour without feeling fatigued. I quickly adapted to the H1 — after only a few minutes, I felt as comfortable with it as with instruments I've played for years.

The unit I tested had Physis's PD3 pedal unit plugged into it. This three-pedal assembly felt solid, and although it sat on a hardwood floor, it stayed in place nicely as I played. It offers half-pedaling, and plays back the sound of damper felts being lifted off the strings when the sustain pedal is depressed. Overall, the H1 felt solidly built and of high quality.

Because the H1 is Physis's stage model and is designed to be plugged into a PA system, it lacks built-in speakers. Physis offers the ST1 stand with built-in pedals and speakers, and SP2 speakers, which can be mounted on the ST2 stand. Physis also offers several other stage pianos, including models with fewer than 88 notes, as well as one in a traditional vertical piano cabinet with built-in speakers.

The Sounds

The H1's three families of physically modeled sounds include: acoustic pianos; electric pianos, including Rhodes stage piano, Wurlitzer A200, and Hohner Clavinet; and mallet instruments, ranging from xylophones to vibraphones. Each family has 32 permanently stored sounds, as well as copies of them in 32 user-rewritable locations in its memory, for a total of 192 sounds. There are also 192 PCM samples of electric and pipe organs, harpsichord, basses, guitars, pads, and string and brass ensembles. Editing sounds on the H1 is simple thanks to a well-laid-out user interface that often graphically depicts changes in the model's parameters. Instruments based on physical modeling are sometimes difficult to use because it's possible to change an instrument's parameters in such a way that it produces a highly undesirable sound or no sound at all. The Physis designers have done an excellent job of constraining the H1's parameters to a useful range. It's worth noting that adjusting parameters of the H1's modeled instruments causes the sound to momentarily mute while the physical model is updated in the unit's processor. While this wouldn't be a problem for most users, it might be undesirable in live performance.

The piano sounds are excellent, and really shine in the bass register. They are full and bright without being harsh, offer a pleasant blend of overtones, and span a wide variety of sounds appropriate for just about any playing style, including pop, jazz, and classical. In addition to acoustic-piano sounds, the H1's modeled electric-piano and mallet-percussion sounds are also standouts. The Rhodes sound nicely stood up to the sound of my restored Fender Rhodes Mark I stage piano, offering all the bite and bark you'd expect in the low register, and the smooth, bell-like tones in the midrange. I found the bass guitar and guitar sounds quite serviceable, although the guitar sounds in particular sounded a bit synthetic. If the H1 has a weak spot, it's in the ensemble sounds. The string, brass, pad, and choir sounds were all rather synthetic and static when compared to the modeled sounds. However, any of the ensemble sounds could be useful when layered with the excellent modeled piano, mallet, and electric-piano sounds.

I was delighted to discover that the H1 offers extensive tuning capabilities: the user can individually tune each key on the keyboard. It also offers a few different popular preset historical temperaments. With the ability to change both the tuning stretch curve and how in tune the keys are with each other, the H1 does a great job of allowing users to design anything from an out-of-tune bar piano to an avant-garde microtonal creation.

Physis Piano's H1 is a strong contender in the digital-piano and stage-piano markets, and worth considering if you're in the market for a great-sounding and unique instrument.

Physis model specifications

Note that models, prices, and specifications may have changed since this article was first published. See www.pianobuyer.com for current information.