Cross-relation
Chromatic contradiction of a note between two voices in successive chords.
What it means
A cross-relation (false relation) arises when a note appears in one voice in a chord and in the following chord appears chromatically altered in another voice, for example F in one and F sharp in another voice. The two voices contradict each other chromatically, without a transition in the same voice in between.
Musical use
In strict theory the cross-relation counted as a fault, because it sounds harsh and unclear. English composers of the Renaissance and baroque, including Thomas Tallis, William Byrd and Henry Purcell, on the contrary used it deliberately as a means of expression; one speaks of the "English cadence". In Romantic music too it creates colored tension.
The cross-relation should be distinguished from chromaticism within a voice, in which a note is raised or lowered smoothly, and from dissonance between simultaneous notes, whereas the cross-relation takes place between successive chords.
Performance practice
When you sing a cross-relation, pay attention to clean intonation of both notes: they should remain clearly distinguishable. Give the passage weight, since it is often a high point of expression.