Generally, one of the instrument voices used most frequently is the piano. There is a great deal of variation in "good" piano tone. Many players like a bright, crisp sound, while others prefer a mellower tone. Some like a great deal of harmonic content, others a bell-like clarity with fewer harmonics. Whatever your preference, will you be satisfied with the piano sound of the model you're considering?
Many instruments sound slightly different as a note begins to play. For example, a flute takes a quarter of a second or so to build up enough air pressure to reach the pitch of the note, resulting in a "breathiness" to the sound. The same is true of many other wind instruments. Guitarists and other players of stringed instruments "bend" notes by varying their touch. Jazz organs often have a percussive "pop" at the beginning of the note. How well do the digital voices of the model you're evaluating emulate the actual instruments?
Even entry-level standard digitals include such effects as Reverb and Chorus. More sophisticated models have many other effects, as described in the "Digital Piano Basics" articles. Having heard them demonstrated, do you think these effects will be useful to you?
Take your time. Following the salesperson's demonstration, most dealers will let you spend time experimenting — although some may prefer that you use headphones.
Aside from sound, the most important element in the selection of an instrument is likely to be the feel of the action. Unless you're considering only digital pianos that employ an actual acoustic action (see "Hybrid Pianos," elsewhere in this issue), you'll be selecting from a variety of actions that all try to emulate the feel of an acoustic action. The aspect of action feel that seems to generate the most discussion is whether the touch weight is light or heavy, and which is better. This is covered in more detail in "Digital Piano Basics, Part 1," but here's the bottom line: Just as there is no single correct piano sound, there is no single correct touch weight; rather, there is a range of acceptable touch weights. If you spend the majority of your playing time with a heavy action, when you encounter an instrument with a lighter action, be it acoustic or digital, you'll play too heavily — and vice versa. The only cure is to play as many instruments as possible, as often as possible. Listen to how each piano responds and adjust your touch accordingly. You've probably driven cars with light steering and cars with heavy steering, and generally managed to avoid hitting any trees with either of them. With varied experience, you learn to adapt.
Common to acoustic and digital actions is mechanical noise. Digitals are frequently accused of having noisier actions because their sound can be reduced to a whisper or played through headphones, leaving the action noise audible, whereas the sound of an acoustic piano tends to always mask its action noise. This is not to say that some digital actions aren't unusually noisy, but to honestly compare them, you have to play them with the volume turned off. In addition to letting you compare action noise, this prevents your mind from judging the feel of an action based on the tone of the instrument.
New or Used?
Because digital technology advances at a blistering pace relative to acoustic-piano technology, there is much less interest in used digitals than in used acoustics. Many of today's digital pianos eclipse the capabilities of the models of even five years ago. Combine this technological advancement with the fact that support of older instruments may be limited — after production of a particular model ceases, electronics manufacturers are required to maintain replacement parts for only seven years — and investing in older models becomes worthy of serious second thoughts.
Owner's manuals no longer accompany many used instruments. If you find an interesting used instrument, make sure that the manual is either still with it, or is readily available from the manufacturer or on the Internet. The manual is your best tool for ensuring that everything on the instrument still works correctly. It's not simply a matter of pressing every key, button, and pedal to see that they work; to thoroughly check the instrument, you also need to know what some of the less obvious controls are supposed to do. None of this is to say that used instruments should be avoided — I've played ten-year-old digital pianos that worked perfectly. But when considering an older digital piano, extra care should be exercised.