There are many ways you can participate during ensemble improvisation. Each approach adds a different facet to the sound, and each requires a distinct set of skills on the part of the player.

Playing a Solo

Playing a solo is the first thing most people think of when they think of improvisation, because the person taking the solo is always the featured musician at the moment they are soloing, while the other musicians are taking a supporting role.

In simple terms, improvising a solo consists of listening to the rhythm and the chord progression that are being played by the band, and creating on-the-spot melody lines over those sounds. Improvised solos are scale-driven, meaning that the soloist must first know what key and what types of scales fit over the chord changes in order to improvise over those changes using notes that are appropriate.

When soloing over major-key blues or rock chord changes the go-to scales are the pentatonic scale and the blues scale, a close relative of the pentatonic. You'll recall that this is done by playing cross harp, or second position, and by playing a key of harmonica that's three notes above the key the song is in, such as using an A harp to play over changes in the key of E.

When soloing over folk songs or traditional music in major keys the scale to use is the major scale, using a harmonica that's in the same key as the chord progression. Remember that all the notes of that major scale are available to you when you play using holes 4, 5, 6, and 7.

When it's time to solo over blues, rock, or folk songs that are in a minor key you'll need to use a minor scale, which is played using a harmonica that's one whole step below the key of the chord progression (for example, an F harp to play in G minor), and by playing draw harp in third position.

Playing Accompaniment/Comping

While playing accompaniment to the soloist might not seem quite as glamorous as taking the solo, the role is equally important to the final sound that is generated by the band. You'll recall that accompanying the soloist is known as “comping,” which is short for complementing the musician taking the solo.

The role of the players who are comping is to do everything they can to make the soloist sound as good and as exciting as possible. To accomplish this you want to play notes, chords, or phrases that not only enhance what the soloist is playing, but also raise the soloist's level of excitement in order to spur her on to greater heights in her solo.

Comping on the harmonica poses a particular set of challenges. Because the harp is usually positioned as a soloing instrument, if you start to play during somebody else's solo you tend to draw attention away from the solo — a no-no, because it's also very important in comping not to play anything that distracts attention from the soloist. But there are still ways the harmonica can comp effectively.

One way is to find a pattern to accent the rhythm while playing short staccato chords. The term staccato means to hold a note or chord for as short a duration as possible, like a short burst of sound. This is the opposite of notes written with a slur, which are intended to be strung together into one smooth sound — staccato notes are meant to be choppy and detached from one another. As an example, the harp might play short staccato accent chords on beats 2 and 4 of the measure, doubling the same chords that are being played in the chord progression.

Another way the harmonica can comp is to pick a note or chord and hold it for a long, extended time to create an organ-like background to the chord progression.

These are by no means the only ways for the harmonica to comp, so spend some time thinking of other ways you can make yourself effective, as well as listening to recordings to see how other harp players function under those circumstances.

Adding a Sectional Part or Rhythmic Accents

Another option when comping is to introduce a whole new part or feel to the music, as if you were adding a horn-section part. One example of this is to add a short, repeating chord phrase on every fourth measure of a 12-bar blues, such as:

A sectional part like this repeating chord phrase adds excitement to the chord progression and also provides a rhythmic kick into the first measure of every line.

Rhythmic Alterations or Overlays

Still another way to go when comping is to add a rhythmic alteration or overlay to the existing rhythm. A rhythmic alteration would be something like adding a strong accent to one of the existing beats of the rhythm, such as accenting beats 2 and 4 of each measure. A rhythmic overlay would involve playing a separate new rhythm over the existing rhythm to form a polyrhythm. A polyrhythm is two or more rhythms being played at the same time. An example would be playing a triplet feel over straight 4/4 time, so that you were playing three beats for every beat of the 4/4 measure. Either of these approaches adds to the rhythmic interest of the music and provides the soloist with more options to play off of.