Partimento: improvising over a given bass

We often forget it: Bach, Handel, Mozart and Beethoven were first famous as improvisers. In the conservatories of 18th-century Naples, students learned to improvise with partimenti: simple bass lines, sometimes figured, over which they had to realise harmonies, then melodies, then whole pieces. This method is making a strong comeback today, because it ties together harmony, keyboard and invention.

1. The rule of the octave

How do you harmonise a bass moving up or down by step? The Neapolitan masters fixed a standard chord for each degree of the scale: the rule of the octave. Ascending, in C major:

The figures show intervals above the bass: 5/3 = triad in root position, 6/3 = first inversion, 6/4/3 and 6/5/3 = inversions of seventh chords. Degrees 1 and 5 carry the stable chords; the others are "passing" chords.

M:4/4
L:1/4
Q:1/4=72
K:C
%%staves {RH LH}
V:RH clef=treble
V:LH clef=bass
[V:RH] [EGc]2 [FGB]2 | [EGc]2 [Acd]2 | [GBd]2 [Acf]2 | [Gdf]2 [Gce]2 |]
[V:LH] C,2 D,2 | E,2 F,2 | G,2 A,2 | B,2 C2 |]

2. From skeleton to melody: diminution

Once the harmonies are in place, you ornament the upper voice: this is diminution. You replace a long note with several shorter notes circling around it: arpeggios, passing notes, neighbour notes. Here is an eight-bar minuet bass with, first, a "skeleton" upper voice:

M:3/4
L:1/8
Q:1/4=108
K:C
%%staves {RH LH}
V:RH clef=treble
V:LH clef=bass
[V:RH] e6 | f4 d2 | c4 A2 | B6 | G4 c2 | a2 f2 B2 | d6 | c6 |]
[V:LH] C,4 E,2 | F,4 G,2 | A,4 F,2 | G,6 | E,4 C,2 | F,2 D,2 G,2 | G,4 G,,2 | C,6 |]

Then the same bass with a diminished (ornamented) upper voice:

M:3/4
L:1/8
Q:1/4=108
K:C
%%staves {RH LH}
V:RH clef=treble
V:LH clef=bass
[V:RH] e2 g e c2 | f2 a f d2 | c2 e c A2 | B2 d c B A | G2 c e g2 | a2 f2 B2 | e2 d2 B2 | c6 |]
[V:LH] C,4 E,2 | F,4 G,2 | A,4 F,2 | G,6 | E,4 C,2 | F,2 D,2 G,2 | G,4 G,,2 | C,6 |]

Each skeleton note is still present on the strong beat (or nearly); the other notes are chord arpeggios (bars 1-3) or passing notes (bar 4). In bar 7, the E over the G bass evokes the cadential six-four, resolving to D and then B.

3. Diminution formulas to know

• Arpeggio: the chord tones in any order.
• Passing note: connects two chord tones by step.
• Neighbour note: step away and back (E-F-E).
• Appoggiatura: a non-chord note on the beat that then resolves (very expressive, typical of the galant style).
• Sequences: the same formula repeated on each degree of a rising or falling bass.

Exercise: your first improvised minuet

Start the ballad track in C for mood and tempo, or play alone with the metronome at 100 to the quarter note.

1. The bass alone. Play the minuet bass several times, singing the skeleton notes.
2. The skeleton. Hands together, skeleton version. Then invent your own skeleton: one chord tone per bar (or two), moving by step as much as possible.
3. One formula. Ornament your skeleton with a single formula for 8 bars (for example: arpeggios only).
4. Mix. Arpeggios, passing notes, neighbour notes. Keep bars 7-8 as a fixed cadence.
5. Form. Play the 8 bars twice: first a simple diminution, then a more ornate one. You have a minuet shape (with a varied repeat!).