Where does tonic collide?

In music theory the tonic is the central note of a key, the first degree of the scale that the other notes are heard as leaning toward and resolving to. Rameau's 1722 Traité de l'harmonie placed this central note at the root of tonal harmony, treating it as the pitch from which a key takes its name and to which its cadences return. Krumhansl and Kessler's 1982 study later showed that listeners rank the tonic at the top of a stable hierarchy of pitches within a key. The referent here is a point of rest in a system of pitches, not a sustained pull in a muscle or a stressed unit in speech.[1][2]

Unit

One pitch class designated as the first scale degree that names and centres a key

Recovery means

Not applicable

Measured by

Identified from the key signature and from cadential resolution, and probed by tonal-hierarchy and probe-tone experiments

In physiology a tonic contraction is a sustained, continuous state of low-level muscle activity, the steady background tension often called muscle tone, in contrast with brief phasic contractions. Sherrington's 1906 The Integrative Action of the Nervous System analysed reflex tonus and the way the nervous system maintains this ongoing postural tension, setting it apart from rapid, transient movement. The referent is a lasting physiological state of a muscle held by continuous nerve activity, not a resting note in a key or an accented unit in a spoken phrase.[3]

Unit

A sustained level of muscle tension, scaled by force or by continuous electrical activity in the muscle

Recovery means

Tension subsides as the sustaining reflex or motor drive is withdrawn

Measured by

Recorded by electromyography and by measuring resting muscle tone or resistance to passive stretch

In phonetics the tonic is the syllable that carries the main pitch movement of a spoken phrase, the most prominent, accented syllable around which the intonation of the group is organised. Halliday's 1967 Intonation and Grammar in British English named this the tonic syllable and made it the anchor of the tone group, the place where the principal fall or rise is realised. The referent is a point of prominence in the stream of speech, not the home note of a musical key or the sustained tension of a muscle.[4]

Unit

One syllable per tone group marked as the carrier of the main pitch movement

Recovery means

Not applicable

Measured by

Identified by ear and by acoustic analysis of pitch, duration, and intensity as the point of greatest prominence