Chord-Tone vs. Chord-Scale Soloing
For the past few decades or so, more and more jazz players have been using the chord-scale approach for soloing over chords in progressions. The chord-scale approach is based on the idea that if a chord is diatonic to a scale, then that scale can be used as a source to derive melody on that chord.
Using the chord-scale approach gives improvisers (especially less proficient ones) greater melodic and rhythmic mobility (i.e., they can improvise pitch sequences in eighth notes, triplets, sixteenth notes, etc.). Whereas chord tones must be played in leaps (minor third intervals or wider), a chord scale can be played in steps (major and minor second intervals), and consecutive steps are much easier to play fast and accurately than consecutive leaps. In general, less-experienced players are also familiar with scales and scale patterns than chord arpeggios from practicing technical exercises in method books and, therefore, prefer to use chord scales for improvising.
A chord scale contains not only the tones of the chord to which it is applied, but also the tensions. Therefore, by improvising on a chord using a chord scale, the soloist will almost certainly play some chord tones and some of the more colorful notes (tensions) as well. It is likely that without the help of chord scales, a soloist may not know (i.e., be able to hear) specifically what tensions fit the chord tones appropriately in a particular harmonic context.
So, in a sense, chord scales do the work of and for the ear. They enable an improviser to play active melody lines that not only agree with the chords, but also contain the more colorful melody notes (i.e., notes other than chord tones) that the player may not be able to find or select by ear alone.
However, for beginner and intermediate-level players, the chord-scale approach has a potential downside. Many students begin studying chord scales early in their musical education and attempt to apply the knowledge acquired immediately on their instruments. Unfortunately, this often happens too soon in the student's development as an improviser--before he or she has learned how to shape an appealing improvised melody by ear on a chord or chord progression using only, or mainly, chord tones.
Chord scales can present too much information, or information that cannot be readily processed, controlled, and used musically by the novice improviser. It is much easier to understand chord-scale theory than it is to apply it with musical results in an improvised solo. Improvising on chords with chord scales means that a soloist can play melody notes that he or she does not recognize or cannot identify and control by ear. This can result in wandering, shapeless, directionless, or mechanical-sounding melody lines. Often the lines are played in eighth notes to the exclusion of all other rhythm values, producing undesirable melodic and rhythmic content. Such improvised melodies often tend to outline tonic quality on nontonic functioning chords and vice versa.
Direction changes in the melodic curve are also somewhat less frequent because the rhythms are predominantly eighth notes and are less noticeable because of the predominance of stepwise motion. (Melodic intervals wider than a second or a third are less common if not rare in elementary-level improvised solos using the chord-scale approach.) This produces a consistently linear melodic line that sounds limited or uninteresting because it is not balanced by more angular melodic curves.
It is relevant to point out here that the pioneers of jazz improvisation relied on their listening/hearing skills and their ability to accurately outline basic chord sound to guide their improvising and to create inspired melodies. They did not rely on the mechanics of chord scales. Beginning improvisers should, therefore, first experience how good it sounds and how right it feels to play inside the chords using only the chord tones before experiencing the allure and sophistication of chord scales. Improvising melodies using only chord tones connects the soloist to the song's harmony, giving him or her a feeling of oneness with the music. This is essential before a player can hear how to use chord scales and nonharmonic approach notes effectively.
Ideally, melodic ear training for improvisers should begin with chord-tone soloing and then advance to chord tones with approach notes and/or chord scale soloing. The musical example is a chord-tone solo on the progression of a well-known standard tune.