Two-Part Invention No. 8 (F major, BWV 779)

Background

Johann Sebastian Bach's fifteen two-part Inventions began life in the Clavier-Büchlein, the keyboard notebook he started in 1720 for his eldest son, Wilhelm Friedemann, where each was headed Praeambulum, a prelude. When Bach made a fair copy of the set in 1723 he renamed them Inventio and arranged them in rising order of key: C major, C minor, D major, D minor, and so on up to B minor, fifteen keys with no more than four sharps or flats. The F major Invention, BWV 779, is No. 8 in that order. (The set's purpose is described on the Invention No. 1 page.)

What sets No. 8 apart is how strictly it begins. For its first several bars it is a canon: the left hand plays exactly what the right hand played one bar earlier, an octave lower, like a round such as Frère Jacques. Bach then loosens the rule, sends the theme through other keys and brings it home to F major. The theme is easy to spot, because it leaps upwards in broken chords before running down a scale, so you can hear every new entry.

How to practise it

The Invention is in 3/4 and has 34 bars. The right hand starts alone, after an eighth-note rest:

In bar 1 the thumb stays on F while the other fingers reach for A, C and then the high F; the hand opens to an octave without moving. In bar 2 the run uses 5-4-3-2-3-2-1, then finger 3 crosses over the thumb, ready to land on F in bar 3.

The left hand enters a bar later with the same notes:

Because the hands play the same music at different times, playing them together can feel like patting your head and rubbing your stomach. These steps help:

1. Each hand alone, two bars at a time, with the same fingering every time. Write it in.
2. Play the right hand while humming the left-hand line, then the other way round.
3. Hands together, bars 1 to 4 only, very slowly, listening for the echo.
4. Bars 4 to 7, full of sixteenths that rock to and fro (A, C, B flat, C in the right hand in bar 4). Keep the wrist loose; fingers 1-3-2-3 suit the pattern.

A common way to play Bach's quick pieces on the piano is with the eighth notes slightly detached and the sixteenths smooth. Whatever touch you choose, keep it the same each time the theme appears, so the listener can follow the canon.

Tempo ladder: 50, 60, 72, then the full 84 beats a minute. The mood is sunny and lively: let each new entry of the theme come forward a little, and keep the hand that is not leading lighter.