As a form of musical “play,” improvisation often involves significant amounts of iteration and experimentation. Think of a child who begins designing an airplane out of LEGOs. At first, the basic structure is formed, and over time, new bricks are added to create special features. Sometimes, a child must try different combinations of bricks to get just the right result. None of the choices made along the way are right or wrong, but they are all essential steps to getting a satisfying result.
Similarly, improvising a bass line to a given melody is a creative, playful activity that will involve significant iteration and experimentation. As you begin trying different possible approaches, you may find that a simple melody admits seemingly countless possible bass lines.
Before you begin, it is important to remember three functions of a bass line, the last two of which are unique to this line as the lowest in the texture. First and foremost, the bass line should itself be a beautiful and musically appropriate addition to the melody. While defining these criteria is somewhat subjective, for now, it is worth noting that the process of improvising a bass line should avoid defaulting to formulas or patterns. Further, we are improvising a bass line, not just the bass notes to whatever harmonies you think the melody calls for. Often, a good bass line will create harmonic possibilities that you hadn’t considered, so at this stage, it is best to think of the bass line as a second melody that will complement the given melody.
As noted, there are two special functions that the bass line plays. The first is to establish a beautiful contrapuntal relationship with the melody. Contrapuntal writing has a long history stretching from the Renaissance through the compositions of contemporary composers. While counterpoint is sometimes approached as a rules-based compositional practice, the basic aesthetic values of contrapuntal writing, including balance, flow, and independence of voices, are typical across styles. When improvising a bass line in a tonal context, consider some of the musical qualities that are associated with each of these aesthetic qualities:
|Does my bass line complement the rhythmic structure of the melody by using similar rhythmic durations?
Does my bass line have a clear overall shape, with points of arrival?
|Does my bass line use mostly stepwise/conjunct motion?
Does my bass line approach large leaps with care (often following them by stepwise motion in the opposite direction)?
|Does my bass line use different rhythmic patterns from the melody?
Does my bass line establish a contour that is unique from that of the melody?
Does my bass line use some contrary motion by sometimes moving in a different direction than the melody?
Does my melody establish mostly consonant relationships with the main, structural notes of the melody?
When I use dissonance, does the dissonance resolve satisfyingly?
Are there places in which a chromatic passing tone between scale steps could add a special color to the bass line?
The second special function played by the bass line is to steer the direction of the phrase toward its endpoint. In tonal music, most melodies conclude by suggesting an authentic cadence. Establishing an authentic cadence would typically demand ending the bass line with scale degrees 5-1/sol-do. Before the cadential scale degree 5/sol (which suggests a root position V chord), you might consider whether or not scale degree 5/sol can be preceded by scale degrees 2/re, 4/fa, #4/fi, or some combination of these scale degrees (e.g., scale degrees 4-2/fa-re, scale degrees 4-#4/fa-fi). These bass notes are often, but not always, used to prepare for the arrival of the bass note sol. Once you have a sense of how your bass line will end, consider how your bass line will establish and prolong the opening tonic. Also, consider whether your bass line will wander far from tonic before arriving at the predominant and cadential bass notes.
Taking those contrapuntal and phrase-specific considerations into account, it is time to begin the process of improvising!
Here are some strategies to get started:
- Try using a minimal approach by singing and sustaining only do from the beginning until you get to the cadential dominant. Then, switch to scale degree 5/sol, and then return to do in the bass when the melody concludes (usually on scale degrees 1/do or 3/mi). Try this a few times, and as you improvise, consider if there is a fitting location to add a predominant note in the bass (scale degrees 2/re, 4/fa, or #4/fi).
- Begin iterating on the minimal approach by listening for structural notes in the melody (often notes on strong beats) and finding consonant intervals below them that you could move to from the sustained do.
- As you sketch out basic contrapuntal possibilities, consider some of the aesthetic questions above and use these considerations to spark new ideas and approaches. For example, if the melody started with an ascending gesture, can you move in the opposite direction and descend to the next structural note? Is there a shape you would like your bass line to take? Are there any moments where you can use a dissonant interval and resolve it satisfyingly?
- Once you have a basic contrapuntal structure established, begin to increase rhythmic variety by adding embellishing tones to your bass line. Try to create movement in your bass where the melody is less active and vice versa. Ideally, the bass line will project independence from the melody without stealing the show. That said, this is your music, so have fun and see how far you can push the music’s boundaries…and your own!
- As with all musical performances, improvisations should strive to exhibit poise and control. As you improvise a bass line on your voice or instrument, always keep your ear in control by audiating each note before you perform it. Letting your ear guide your performance will ensure that this activity results in maximal growth.
To practice, take any simple song (e.g., a children’s song or folk tune) and learn to play it on some instrument (perhaps the piano). As you play the song, try singing an improvised bass line to the melody. Try each melody several times so that you can work through the strategies above. You can also flip the part assignments by singing the melody and playing the bass line. Feel free to use a device to record your performance of the melody if performing two melodies proves too difficult.
Another excellent use of this skill is to improvise a bass line along with the music you are learning in private lessons, large ensemble, and/or chamber music. After you create different bass lines, return to the original score to study the composer’s bass line. Often, engaging creatively with the music you are learning can reveal new things about the choices made by the composer.