Ensemble Activity: Laid Back, a little bit

Two weeks ago I introduced the percussion concept of 'laid back', where an instrument sounds late to very late relative to the central the beat. In truth some participants had already achieved this, albeit inadvertently, last month (see: http://salsadiary.blogspot.co.uk/2017/02/ensemble-activity-strictly-in-pocket.html Exercise One, Result 2).

Although they'd become comfortable with the practice format, the ability of play late on the beat as a synchronised ensemble still eluded them. Whenever the 'laid back' call was issued from a well-synchronised 'in the pocket', the unit dissolved quickly into a mish-mash of lates.

I can only put that down to different individual offsets.

Offset: A physiological phenomenon
If a motor signal is issued from the brain to the arms and legs at the same time, the arms will move before the legs will. This is because:

1. the signal path lengths are shorter to arms than to legs; and,
2. arms have lower mass than legs and so can accelerate more quickly.

α-motorneurones have a nerve conduction velocity range of between 80-120 metres per second. That sounds really quick, but if there is a half-metre difference in signal path length between arms and legs, there would be a lag of at least 4/1,000s of a second (by simple calculation) and that's the best-case scenario. It might not sound like much, but that's the difference between an 'in the pocket' and a 'slightly late' attack. In practice, I see offsets in the order of tens of thousands.

So, if two concurrently-timed signals are issued from the brain to the arms and legs, and the arms play the maracas very late on the beat, the legs will step off-time. This is the challenge of playing and dancing late: there has to be near-zero offset.

Near-zero offset can only be achieved by sending impulses to the legs BEFORE impulses to the arms.

A mish-mash of lates
The phenomenon of everyone playing different interpretations of 'late' is unsurprising given the factors stacked against them, different perceptions of beat; signal path lengths; limb masses; and conduction rates.

The efforts where valiant, and occasionally successful. However at the third session of asking it was time to change tack. Instead of going the whole hog, as we did with the push, I started using the cues "slightly late of pocket" and "a little later". My scientific self wrinkled its nose at the arbitrary terms (how late is slightly late?) but the change worked. It got participants to play later synchronously.

We'll have to inch our way to the back of the bus.

Loo