Even within a single work we can find different points along this continuum, and this is the case with The hour of the soul. Gubaidulina’s concerto for percussion and orchestra provides a compendium of her aleatory techniques. Example 1 contains the first measure of the work, which is performed by the percussion soloist on the timpani.
Example 1:
The determination of many of the musical parameters in this measure is left to the discretion of the performer. Gubaidulina specifies the instrument and the pitch. For several of the figures, she specifies how many notes are to be played in each group and where the silences are. The durations of the silences differ, but they are relative to one another and no metric is specified. Dynamics are specified, as are crescendos and diminuendos, but dynamics are one of the most subjective musical elements. This opening measure ranges from pp to mf, which is a fairly narrow range. Accelerations and ritardandos are shown, but the pacing is left up to the soloist. The duration of the measure is also indeterminate.
Most of the solo percussion passages until rehearsal cue 14 are similar in design to the first measure. The instruments involved to this point (timpani and then temple blocks) have a limited number of pitches that they can sound: a timpani ordinarily can sound one pitch at a time and Gubaidulina calls for five temple blocks. Near rehearsal cue 14, the percussion soloist moves to the cimbalom. The cimbalom, which is like a hammer dulcimer, has a much wider range than any of the previous instruments (D to e’’’). Gubaidulina does not use a clef for this instrument; rather, she indicates the gamut of the instrument with a graphic consisting of a vertical line with a triangular point at the top and bottom. For the most part, her notation for the cimbalom leaves specific pitches to the discretion of the performer. There are four types of notation that she uses in the cimbalom part, as show in Example 2.
Example 2:
In Example 2, the notation in the first measure that the cimbalom plays (the next-to-last measure of the example) consists of a curvy line, signaling a glissando with no specific beginning or ending point. We can assume that the ending of the passage should be substantially higher than the beginning was, and that the beginning is followed by a slight descent in pitch before the overall ascent. Dynamics are specified. There is no rhythm in the measure: the nature of a glissando is not rhythmic. Instead, the duration of the glissando is delineated by the barlines, with a short pause at the end of the measure. In the last measure, the rhythm is specified, as are dynamics. The contour of the line, which falls over time, is indicated, but no pitches are specified.
Example 3:
In Example 3, which comes from rehearsal cue 23, the durations of the glissandi are specified by the notes underneath the staff. Example 4 shows the four measures before rehearsal cue 29. Here, the rhythm is clearly specified, as are the dynamics. Gubaidulina calls for large clusters of pitches to be performed, and the relative register of these clusters relative to the range of the cimbalom and relative to one another is the only information given.
Example 4:
Example 5:
A third type of indeterminacy occurs beginning at rehearsal cue 31. The passage appears in Example 5. Gubaidulina writes a non-metrical passage and writes passages of different durations for the solo percussionist and three solo first violinists. The musicians are instructed to repeat their material over the course of the unmeasured passage. In contrast to the first measure of the piece (discussed in Example X above), Gubaidulina specifies a duration for this passage: the episode lasts for twelve seconds. There might be a practical reason for specifying a duration here: several instrumentalists are involved and the conductor needs some way to coordinate the instrumentalists.