Composing a Ground Bass
A ‘ground bass’ is a short bass line (usually 4
to 8 bars long) which is repeated constantly throughout a piece.
While the bass stays the same, the melodic voices develop and change
above it. A good ground bass piece
will have a clear, simple bass line, with imaginative development of the upper
parts.
There are lots of good examples to listen to, especially from the Baroque period of Music History. You can find links to some MIDI files at the bottom of the page.
Here is a step by step guide to writing one, along with illustrations of how Pachelbel did it in his Canon in D - one of most famous ground bass compositions in the repertoire.
Step
One - Make
up the bass part. It should be:
- either 4
or 8 bars long
- not too
fast or complicated
- easy to remember – try to use a recognizable rhythmic pattern
This is Pachelbel's ground bass. Click on the score to hear it play.
Step
Two - Work out the chords which go with your bass line.
(You don’t have to play them the first time through, but you can if you
think it sounds better). Aim for:
- One or two
chords per bar
- chords that are
built on notes in your bassline
This is Pachelbel's. Some performances just use the bass line at first, while others spread the notes of the chord, like this, to make the texture more interesting.
Step
3 - Make up
your first variation. This will
consist of
-
your bass part
-
a simple melody based on the chord sequence
-
(optional) chords to fill in the gap between the bass and the melody
Pachelbel's melody just takes one note out of each chord and arranges them into a melody. Notice how they are chosen to make the melody as smooth as possible.
Step 4 - make up the next variation. You have several options how to do this:
- Continue your melody from variation
one to make it twice as long
- Repeat variation one, but add a
second layer of melody (a counter-melody)
- Vary the melody from variation one
by using faster notes
- Vary the melody from variation one
by changing the rhythm
- Leave the melody out, and add an interesting rhythmic pattern with the chords
Pachelbel goes for option 2, adding a second instrumental part to variation 1. (Actually the two violins are playing a round - this is what the title "canon" means)
Step 5
- Keep adding variations, so that there is a sense that the piece builds
up steadily to a climax. Use as
much creativity and imagination as you can!
Most ground basses use all the techniques in step 4 at some point.
Pachelbel starts his gradual build up in variation 3. He adds a third layer of melody, and the first layer now moves in crotchets, twice as fast as in variations 1 and 2.
Pachelbel continues to develop his ideas, and the developments get progressively more complicated as he goes through the piece.
Step 6
- Find a good way of ending the composition.
A simple last variation is usually a good way of doing this – perhaps
just use the bass line on its own, so the piece ends in the same way as it
starts.
After all the musical complexity in the middle of the piece, the last few variations of Pachelbel's canon get gradually simpler, so there is a sense of winding down.
Click here to listen to the whole piece.
Ground Bass pieces - some more examples to listen to.
Beethoven Variations on a theme from Prometheus