Ground bass compositions are based on a bass line that repeats throughout the piece, usually exactly, or nearly so. Many musicians have found this a compelling compositional constraint for keeping themselves … well … grounded!

How many musicians are we talking about? Well, this practice was highly popular in the Baroque (Purcell was a particularly keen and expert protagonist), it is even more common in popular songs of recent years (see Harmonic Schemas in Pop Music), and there are more than a few examples from in between. In short, it is an extremely and enduringly popular form.

It’s easy to confuse “ground bass” with some other terms; going from broad to specific, the key terms to distinguish are:

• Ostinato: any pattern that repeats throughout a long section or whole work in one voice, like the motto side drum rhythm of Ravel’s Boléro.
• Ground bass: a specific type of ostinato in which a bass line repeats throughout a work or section. The work itself can also be called a ground bass.
• Chaconne and Passacaglia (and international variant spellings such as “Chacony”): sub-genres of the Baroque ground bass. Among their other characteristics, both of these two are in triple meter. Every Chaconne or Passacaglia is also a ground bass, and every ground bass is also an ostinato, but the reverse is not true: not every ostinato is a ground bass, and not every ground bass is a Chaconne or Passacaglia.

This chapter provides some files and instructions to help you explore some of the ways to create effective ground bass compositions. We focus on the Baroque model, and on creating variety through re-harmonizing the same bass in different ways and varying the texture.

Multiple Harmonizations of a Given Bass

Continually using the same repeating bass line throughout could get tedious, and is especially liable to make the harmony extremely static. To that effect, inventive composers find ways to re-harmonize the same bass line to move to other keys, or at least hint at such a move. This often relies on seeing the different ways in which a single interval in the bass could be reinterpreted.

While this might not seem like much to work with, this bass harmonization “cheat sheet” (PDF) shows that there are many ways to re-harmonize bass intervals. It is organized by bass interval: both ascending and descending forms of each interval from minor seconds to tritones. Note that this is supposed to help you work out your options—you definitely don’t need to use all of these! We’ll see below how Purcell uses just a few of these to create harmonic variety in a very long work that’s almost entirely in G minor. We’ll be especially interested in moments where Purcell avoids the main perfect cadence at the start/end of each iteration of the ground, joining two grounds together with a subtler seam and thereby varying not only the harmony but also the phrase rhythm of the piece.

Analysis: Purcell’s Sonata in G Minor (Z 807)

To explore some of the options here, let’s take a look at Purcell’s Sonata in G Minor (Z 807). We’ll look at how Purcell uses (extensive) imitation and (occasional) tonicization. All of these matters are also included on the score as text annotations at the relevant moment (Example 1).

Harmony

Harmonically, the piece is resolutely in G minor almost throughout, though Purcell tonicizes several keys along the way, as summarized in the second table below. Notice especially how Purcell finesses that boundary between the start and end of a ground iteration by avoiding yet another perfect cadence in G minor. For instance, see m. 16 and m. 106 for uses of G major as part of V[latex]^4_2[/latex]/v–v⁶, broadly reversing tonic and dominant function, and likewise m. 26 and m. 86 for G diminished as vii^o6–I in F major.

As a wider matter, notice how extensively Purcell uses 5–6 steps in the melodic parts and how this creates ambiguity in the harmony, as in m. 1 and m. 12. Is the 5 or the 6 harmonic, or perhaps both? Is this consistent, or does it change? This all makes it harder to pin down exactly what the harmony is and where it changes, adding ever further layers of interest to the score. It also helps set up the sequences of 7–6 suspensions such as from m. 71.

Imitation

Imitation is prevalent throughout. The melodic imitations are labeled D and C on the score and in the table below. This is short for dux (leader) and comes (follower). For instance, the violin 1 parts starts a melodic line in measure 1 (beat 1), which is imitated by the violin 2 entering in measure 3 (beat 1). Notice from the table how often these imitations start in the same part of the bar. This is consistent with what we discussed in the context of 16^th-century and 18^th-century imitative traditions. Entering on equivalent beats leads to temporal gaps between entries of three or six beats (beat gaps on the table). Note the many exceptions where Purcell uses closer imitation.

As the score and first table show, there is a great deal of imitation in this piece; almost every iteration of the ground is accompanied by a new imitative relationship in the upper parts (the exceptions are given in the second table below). Perhaps the two most special and interesting cases are:

1. the double imitation starting in m. 196 and imitated with parts swapped in m. 201
2. the imitation of the ground itself in the violin 2 part at m. 99/102

The second table summarizes the iterations without imitation.

Rhythm and Meter

Finally, note how Purcell continually varies the rhythmic values (metrical levels) involved, using a wide range of options. This includes introducing continuous eighth notes (m. 36), sixteenth notes (m. 81 and m. 146), syncopation (m. 126), dotted rhythms (m. 136), and for one passage near the end, changing the notated meter to compound time (mm. 166–185). This is a common device in Baroque ground bass (and other variations-style works of the time); again, these changes usually (but not always) coincide with the start of a new iteration of the ground.

Four Score and More provides several useful files for studying ground bass:

1. Template scores based on Baroque ground bass compositions, but with only the ground bass provided so you can compose a completion of the rest.
2. Those Baroque compositions again, but with the upper parts now included along with annotated files with Roman numerals and more.

In all of these templates and annotated scores, there is exactly one iteration of the ground per system so you can compare equivalent moments directly (vertically). All of these files are available to view online here. Additionally, for direct downloads:

These template scores allow you to try your hand at composing music based on some of the repertoire’s great ground basses.

Take a template and try to compose your own ground bass composition, following these steps:

1. A simple, predominantly diatonic harmonization of the ground, with simple block chords, making sure to follow good voice-leading practice. Use this as a prototype.
2. A set of alternative harmonizations including tonicizations of other keys and re-harmonizations of the first note in particular to vary the apparent phrase length (as discussed above in reference to the “cheat sheet”).
3. Melodic parts that fit with the bass and create more interesting textures. Seek out ways of writing upper parts that can recur in another voice in imitation (and refer back to the Purcell analysis above for ideas!).
4. Finally, combine the best of your ideas into an overall piece that balances textural and harmonic interest and charts an overall trajectory. Why not try a piece with six iterations of the ground, of which the first and last are simple and alike?