Filling In The Gaps
There are instances where the timbalero chooses to play cáscara on the macho [male] higher-pitched shell, and a fill-in rhythm on the hembra [female] lower-pitched shell:
 

Figure 10.12. Cáscara with fill-in
 

The ear training so far has only indicated what a shell tone sounds like, and it is essential for you to know that there is a high shell tone and a low one. As is the nature of AfroCuban instruments, the pailas or timbales consist of a sexed pair of drums:

• the smaller macho which has a higher aggressive tone, and
• the larger hembra which has a lower more mellow tone.

You can vocalise the above rhythm using the syllables 'chik' for beats on the macho and 'ah' for beats on the hembra:

chik-ah-chik-ah-chik-chik-ah-chik-chik-ah-chik-chik-ah-chik-ah-chik-

The cáscara and its 'photo-negative' fill-in rhythm are used together when a light but highly dynamic ride is needed.
 

Clave Ambidexterity
In the interests of balance, I have provided below the cáscara in 3-2 clave orientation.
 

Figure 10.13. Cáscara in 3-2 son clave orientation
 

Referring back to figure 10.4. if we were to accent the second beat of the middle of the three consecutive couplets, we would be marking the start of the rhythmic cycle in 3-2 orientation.

Note: I have chosen to base this tutorial on the 2-3 orientation because of two compelling factors:

1. The similarity between the cáscara and the timbale bell rhythm; and
2. The full agreement between the dance rhythm and the cáscara / timbale bell rhythm on the clave 2-side, which learners find it easier to synchronise to.