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Abstract 0336

Heinonen, Yrjö (1999), "Improvisation and quasi-improvisation — The alteration of chord-based and scale-based guitar solos based on the 12-bar blues progression by George Harrison." Paper for the Summer Jazz Conference 1999. Jyväskylä, Finland, 4-5 June 1999.

The aim of the paper is to explore strategies used in performing a guitar solo based on the 12-bar blues progression. A distinction is made between improvised and quasi-improvised solos. Here the term 'improvised solo' refers to the immediate creation of an entire solo as it is performed, whereas the term 'quasi-improvised solo' refers to the act of performing a beforehand-learned solo with or without elaboration or variation. Cognitive schema theory forms the theoretical foundation of the study. A schema is assumed to activate in two stages: in the first stage a general outline is activated and in the second stage this outline is elaborated. Similar two-stage activation of a schema is also assumed to be apparent in improvisation: first the notes belonging to the underlying chord are activated, whereas the other notes of the scale are activated only later, that is, as the improvisation unfolds in time.

Seven improvised and seven quasi-improvised guitar solos based on the 12-bar blues progression, played by George Harrison, were examined. The frequency of each note of the chromatic scale was counted separately for each 1+12 bar (an upbeat + the 12-bar progression) of each solo. These frequencies were compared on the one hand to a model representing the underlying chord (major triad + minor 7th) and on the other to two models representing the so-called blues scale. One of the blues scale models was taken to represent the pentatonic blues scale (1, 3b, 4, 5, 7b), whereas the other was taken to represent a variant of the chromatic blues scale (1, 2, 3b, 3, 4, 5b, 5, 6, 7b). The playing technique was regarded as chord-based, if the data (the frequencies of the notes) correlated best with the underlying chord model. Correspondingly, if the data correlated best with one of the blues scale models, it was regarded as scale-based.

In the improvised solos Harrison clearly prefers the pentatonic blues scale. Correlation values between the data and the pentatonic model were indeed quite high for each bar of the 12-bar progression. There were, however, a few exceptions to the dominance of the pentatonic scale: (1) the very beginning (upbeat) correlated best with the tonic chord, (2) the ending of the first phrase (bar 4) correlated best with the chromatic blues scale, and (3) the beginning of the second phrase (bars 5-6) correlated best with the underlying chord (IV7b). From bar 7 up to the end of the solo Harrison relies again on the pentatonic blues scale. In the beginning of the third phrase (bars 9-10) the correlation between the data and the underlying chord model was at the lowest but increased towards the end of the phrase. In the quasi-improvised solos a highly consistent alteration between chord-based and scale-based techniques was found. In the beginning of each phrase (bars 1, 5-6, and 9-10) Harrison prefers the chord-based technique, whereas in the end of the phrases he relies on the scale-based technique (pentatonic blues scale). In the beginning of the third phrase (bar 9) the correlation between the data and the pentatonic blues scale model was at the lowest (in fact, it was negative) but increased again towards the end of the phrase. The chromatic blues scale do not play any significant role in the quasi-improvised solos, although there is a slight peak in the end of the second phrase (bar 8).

The tendency to prefer the chord-based technique in the beginning and the scale-based technique in the end of each phrase, which is characteristic of the quasi-improvised solos, fits well to the notion of schema activation in two stages. It also implies that in these solos the schema activation is cyclical, each cycle lasting one phrase of 4 bars. The case of the improvised solos is more complicated, although also here a similar four-bar cycle is evident. In the first phrase of the improvised solos there is a three-stage progression from the use of the underlying chord via the use of the pentatonic blues scale to the use of the chromatic blues scale as the basis of the improvisation. As to these solos, the schema of the first phrase tends to activate in three stages instead of two. In the second phrase a two-stage schema activation similar to the one found in the quasi-improvised solos, involving a change from chord-based to scale-based technique, is evident. In the third phrase the improvisation is based mainly on the pentatonic blues scale. However, the end of the phrase implies a reverse order of the schema activation compared to the quasi-improvised solos and the first two phrases of the improvised solos: what is activated first is the scale and only then the activation of the underlying chord begins to increase.

It may be concluded that Harrison's quasi-improvised solos are more rigid — more schematic, as it were — than his improvised solos, which are evidently more sketchy. In spite of this sketchiness, also the improvised solos show a cyclical schema activation similar to the one evident in the quasi-improvised solos. The main difference between these two kinds of solos seems to be largely in the fact that in quasi-improvised solos each cycle is — in principle — identical (involving a change from chord-based to scale-based technique), whereas in improvised solos each cycle is different from the others. Cognitive schema theory proves to be a relevant framework in studying both quasi-improvised and improvised solos based on the 12-bar blues progression.