Whiter Without The Bombó
While the presence of the bombó was one of the enduring themes in the basslines of the core section, it is important to know that this is not always the case. Indeed the bombó, present or absent, plays its part historically as a defining characteristic between 'black music' and 'white music' in Cuba. Black music was played for consumption by black Cubans, featuring upbeat accentuation at lower tempi. White music was for the Europeanised social elite, played faster and more on the downbeat and backbeat (for more information on this phenomenon, see "Arsenio Rodríguez and the Transnational Flows of Latin Popular Music" by David F. García).

The comparison between the tresillo pattern and the cumbia pattern below perfectly captures the essential differences.

Note: "Cumbia" itself is a non-AfroCuban music and dance genre. I am using the term to describe its typical bass rhythm, which is also expressed in Cuban music.
 

Figure 7.9. Tresillo versus cumbia bass tumbao
 

In the tresillo bass tumbao, the bombó, which accents the upbeat prior to the pulse, creates rhythmic anticipation in every bar. Black dancers through their AfroCuban traditions, had the body isolation skills and the polyrhythmic dance ability to express both the bombó and pulse beat, the lower tempi making this synchopation clearer (see son phrasing and zarabanda tutorials in Rhythm Sense). Typical examples include the music of Cachao's descarga sessions, and that of Arsenio Rodríguez.

With the cumbia-style tumbao, the bass does not generate rhythmic tension. Instead there is a cluster of three evenly-spaced beats spanning two bars of music, with emphasis on the third beat (i.e. the first beat of the new bar). This tumbao can be found in the music of La Sonora Matancera who played guarachas for a predominantly white audience, and in the romantic ballad genre of the Cuban bolero.

Thus in addition to the core material, you would enhance your ability to dance to Latin music if you learned to synchronise your dance rhythm to the cumbia-style tumbao. This would give you access to 'white music' like the boleros of the Puerto Rican Daniel Santos, the Colombian cumbia and Cuban guarachas interpreted in the fashion of La Sonora Matancera.
 

Blackened By The Upbeat
Learning to dance to the cumbia-style tumbao is a fairly simple process. However, doing the same to the black tumbaos of the son montuno is an altogether different proposition. Three tumbaos typical of Arsenio Rodríguez basslines are given below, each one increasingly 'blackened' by upbeats:
 

Figure 7.10. Tumbao variations in son montuno
 

Variation 1
Is the simplest, comprising the classic tumbao on bombó and ponché with an additional note on the pulse beat after the bombó. The bass hence creates the rhythmic anticipation and provides its resolution.

Variation 2
Is identical to variation 1 except that the last note of the clave 2-side is delayed to the upbeat immediately preceding the next bar. This beat is significant in the dancing of the son montuno (see Son Phrasing (Part 3): Son Montuno).

Variation 3
Is identical to variation 2 except there is an additional note on the first upbeat of the clave 3-side. The location of this beat is significant in the AfroCuban rumba, when the vacunao might be performed (see Expanded Glossary). Although no such act is contained in the dancing of the son montuno, urban dancers fluent with rumba may choose to accent this beat.

It is not necessary to clap or mentally play these variations whilst dancing the step rhythm (although that would be ideal). At the very least, you should be able to distinguish the cumbia-style tumbao from the blackened ones, and know why they're played the way they are.