Root (chord) - Assumed Root

An assumed root (also absent, or omitted root) is, "when a chord does not contain a root ( not unusual)," in guitar playing, where the root may or may not be supplied by the bass guitar or another instrument. In any context, it is the unperformed root of a performed chord. This 'assumption' may be established by the interaction of physics and perception (per Hindemith, above), or by pure convention. "We only interpret a chord as having its root omitted when the habits of the ear make it absolutely necessary for us to think of the absent root in such a place." "We do not acknowledge omitted Roots except in cases where the mind is necessarily conscious of them...There are also cases in instrumental accompaniment in which the root having been struck at the commencemnt of a measure, the ear feels it through the rest of the measure."

In guitar tablature, this may be indicated, "to show you where the root would be," and to assist one with, "align the chord shape at the appropriate fret," with an assumed root in grey, other notes in white, and a sounded root in black.

Outside of guitar playing, an example of an assumed root is the diminished seventh chord, of which a note a major third below the chord is often assumed to be the absent root, making it a ninth chord (on ii). However, the diminished seventh chord affords, "singular facilities for modulation," as it may be notated four ways, to represent four different assumed roots, each a semitone below notes present in the chord (D♭ to C).