There are instances of triple metric structures with two triple streams. The time signature for such a structure will most often be 9/8, but examples of other note values like 4 and 16 may replace the 8 in the signature. In 9/8 time, the triple streams will be on adjacent levels, and one or the other will be heard as the beat.
Ex. 43 a metric structure with two triple streams, slower triple stream B as beat
If level B is heard as the beat, as in Example 43, a conducting pattern of 3 can be used. If level C is heard as the beat, as in Example 44, the 3-pattern with a triple subdivision can be used.
Ex. 44 a metric structure with two triple streams, faster stream C as beat
In both of the Examples above, notice that level A is shown with two tied notes. Our notation system is such that a single note cannot represent a measure of 9/8. We can, however, represent this metric structure in 3/4 with a dotted half note as the measure value, three quarter notes as the slower triple stream and three eighth-note triplets as the faster triple stream, as shown in Example 45. This is further confirmation that heard metric structures can be notated in several ways.
Listen to the “9/8 type” examples listed below in Example 46. The clarity and consistency of this metric structure varies considerably within this group. The Mendelssohn piano piece is the most straightforward; the Bach has some subtle duple groups in the slower triple stream near the beginning. The Bartók will require careful listening. In Bye, Bye, Blackbird, the faster stream is heard only intermittently. In the The Boy Next Door, a good deal of music is heard before the second triple stream is introduced. Listen carefully for the entrance of the second triple stream in the Albéniz excerpt.
Ex. 46 Examples of music with two triple streams
1. Triplets in 9/8 Time,
#118, Mikrokosmos B. Bartók
2. Sinfonia no. 6 in E Major J.S. Bach
3. Bye, Bye, Blackbird Joe Cocker
4. The Boy Next Door Bill Evans Trio
5. Asturias (fr. Suite Española) Isaac Albéniz
6. Sadness of Soul Felix Mendelssohn
Metric structures with two non-adjacent triple streams are found in the nineteenth century. Example 47 shows such a structure represented in 3/4. Notice that an eighth-note duple pulse intervenes between the quarter- and sixteenth-note triple streams.
In Example 48, another excerpt from Felix Mendelssohn’s Songs without Words, the two pulse streams are defined in an introduction. The faster stream functions as an accompaniment beginning in measure 7. In the same measure, the cantabile melody, with upward stems, may at first look like another triple stream: a dotted quarter followed by three eighths. However, it will be difficult to hear this pulse, as the quarter note pulse continues to be strongly expressed.
Ex. 48 Mendelssohn, F. The Poet’s Harp, Op.38, No. 3, measures 1-17