pianists have embraced Bach’s keyboard works and rendered them with dynamic nuances that are simply not possible on harpsichord.The piano–initially, “pianoforte” or “fortepiano”–was named such, because it was the first keyboard instrument that responded to the force of the performer’s touch on the keys. Instead of a key “triggering” the plucking of a string, as occurred with harpsichord, a hammer mechanism was set in motion, responsive to the force of the touch of the key.A full range of dynamic levels became possible, from “pianissimo”(“pp,” “very soft”) to “fortissimo” (“ff,” “very loud”). Add to that the beauty inherent in the use of the sustaining pedal, and we can see why pianists would be drawn to the keyboard music of Bach.
ArpeggioLet’s listen again to the first four bars of Bach’s Prelude in C major, following the score as we do.One of the first things that strike us about the piece is the sound of an arpeggio, a broken-chord figuration sounding the notes of a chord one at a time in a repeated pattern. As is often the case, the pattern of the arpeggio is repeated in successive measures, the chord tones changing with the changes of harmony. But what are these chord tones? And what are these chords?These same four bars were presented as a sound recording in Lesson 2, on page “Chord Progression,” cited as an example of the progression: I – IV– V – I. And it’s true: this chord progression is contained in these measures. But there’s more.We know that tonal harmonies are built by stacking successive 3rds above a root. Diatonic triads are built in this way. They consist of a root, a third, and a fifth. What happens, though, if we stack another note a 3rd above the fifth of the triad? That would give us a four-note chord, consisting of a root, third, fifth, and seventh.