The tactus range is also the range of "spontaneous" tempo, that is, of the tempo produced by the typical person asked to tap a steady pulse. This range coincides with a moderate walking pace, a human heartbeat, the rate of jaw movement in chewing, and the infant sucking reflex. It is also a fairly comfortable rate at which to tap a foot or a finger, since it is neither too fast for motor control, nor too slow for accurate, regular timing. Hence the tactus seems to correspond to natural timescales involved with human motion.Vijay S. Iyer
Microstructures of Feel, Macrostructures of Sound:
Embodied Cognition in West African and AfricanAmerican Musics
Tactus is meant to be read aloud. I imagine it introduced by a slow heartbeat that fades in and out.
During the Renaissance, musical tempo was constructed around a time-interval called the tactus. It was the duration of a typical resting heartbeat. The word tactus is Latin. It means contact, or influence, or touch. Some pictures of Renaissance choirs show the chorus members touching each other’s shoulders to tap out the tactus as they sang— sharing, in a way, a single heartbeat by consensus. A note whose duration was one tactus was written as a hollow circle, an o— Today we call this a whole note. So the rhythm of the heart could be written like this: If you play this on any drum-like instrument—say, a table— the pattern will be instantly recognizable to most humans. lub dub ... lub dub ... lub dub ... The first note, the lub, is created when the ventricles of the heart contract, squirting some of the blood backwards into the mitral and tricuspid valves. The flaps of these valves catch the blood, causing them to snap shut. Like a fist pounding on a closed door, the blood reverberates. lub lub lub lub lub The second note, the dub, is created in a similar fashion when back-flows of blood crash into the aortic and pulmonic valves. So really, the sound of the heart is just the slamming of two little pairs of doors ... slam slam ... slam slam ... Now, because the rhythm of the heart is a drumbeat so primal it predates drums themselves, you would think it would merit some sort of name. And by an odd coincidence, the rhythm of the heart is Morse code for the first person singular pronoun: the name you call yourself— affirming that you exist by the very act of keeping you alive. dot dot ... dot dot ... dot dot ... I ... I ... I ...