Recording has been discussed above, in the "Computer Software" section. However, because nearly all digital pianos come with at least basic recording capability, it deserves a bit more attention. You may say that you have no intention of recording your music for others to hear, but in ignoring the instrument's ability to record what you've played, you may be overlooking one of the simplest ways of improving your playing. Whether you're just starting to play or are beginning to learn a new piece, being able to hear what you've just played is a learning accelerator.
I know what you're thinking: "I heard it while I was playing it." While most professional musicians have reached a level where they can effectively split their attention between the physical act of playing the instrument and the mental act of critically listening to what they're playing, few of the rest of us can do this. Recording and listening to yourself will reveal elements of your playing that you never noticed while you were playing, and will allow you to see where to make changes in your performance. This is even more useful when working with a teacher. Imagine listening with your teacher, music score in hand, and pausing the playback to discuss what you did in a particular measure. This is one of many reasons piano teachers are adding digital pianos to their studios; they're great learning tools.
One final thought on recording on the digital piano: Most manufacturers list recording capacity as a certain number of notes — typically in the thousands of notes. But not everyone is counting on the same number of fingers. Recall that MIDI records data "events," including note on, note velocity, note off, program change, control change, and a variety of others, many or all of which could have happened in conjunction with the playing of a single note. Each of these events consumes a certain amount of internal memory. Because this memory capacity is fixed, unless we know which events each manufacturer is counting as "notes," it's pointless to try to decide, based on these specifications, who offers more recording capacity. On the one hand, most instruments have more recording capacity than most owners will use. On the other hand, if recording capacity is important to you, this is another of the many areas in which simply buying the biggest numbers, or the most numbers for the dollar, is not a good strategy for selecting an instrument.
Automated Accompaniments, Chords, and Harmony — the Ensemble Piano
Some people, even some professional musicians, will tell you that using automated accompaniments — those rhythmic combinations of drums, bass lines, and chords — constitutes "cheating." This has never made sense to me. If I use a tool to do something that I couldn't possibly have done with my bare hands, am I cheating?
Whether or not a digital piano has these automatic features, frequently referred to as styles, is the primary factor that separates standard digital pianos from ensemble pianos. If your musical interest is focused solely on the classical piano repertoire, then this capability will probably be of no interest to you. If, however, you or someone in your household plays or plans to play a wide variety of musical styles, the ability to have backup instrumentalists at your beck and call is just entirely too much fun. No matter how good a player you may be, you can't be four people at once — or eight, or twelve, or an entire orchestra. These accompaniments are typically divided into groups by musical genre: Swing, Latin, Rock, World, and so on. The best of these styles are of a caliber that the best record producers would be proud of.
One thing to watch out for is the impact of automatic accompaniments on polyphony (see Part 1). Every bass line, drum beat, string sound, and guitar strum takes a toll on the number of simultaneous notes the instrument can produce. Thirty-two notes of polyphony can get used up in a big hurry when a complex style is playing in the background. If styles are important to you, look for higher polyphony numbers. Also, see if the instrument you're considering is capable of downloading additional styles, and how many styles are available for that model.
How do these styles "know" which key to use when playing all those chords and bass lines? In the simplest "single finger" settings, if the player needs an accompaniment style played in C, for example, she plays a C with the left hand. As chords change in the music, the player makes the appropriate change in the left hand to indicate what the accompaniment should play. Once the harmonies have been determined, the instrument can also apply them to the right hand by filling in the notes of the appropriate chord under the melody note. More sophisticated systems can decipher complex chords by evaluating all of the notes played on the keyboard, so that even advanced players can use the accompaniment styles without being held back from their normal style of playing.