Why Do False Relations Make Two Voices Briefly Clash?

A false relation occurs between different voices: one part has just sounded F while another immediately gives F-sharp, or the two briefly overlap. If a single voice moves by semitone, the ear readily hears a continuous change. When the alteration crosses into another line, the pitches seem to contradict one another, producing a sudden bright sting.

The device is associated particularly with late Renaissance polyphony and with English vocal and keyboard music. It should not simply be treated as a composer's failure to notice the harmony. Each voice may be carrying out a sensible melodic task: one retains the natural pitch of the mode, while another raises the same pitch to sharpen a cadence. The horizontal lines make sense separately; the vertical clash appears where they meet.

When listening, follow the two voices involved before judging the chord. A false relation gains its force not from prolonged dissonance but from rapid resolution. The shadow of the older pitch remains for an instant while the altered pitch already directs the music towards its cadence. Modal colour and cadential direction become audible at once.

At the piano, it is easy to flatten this detail into a single “strange chord”. A better approach is to preserve the independence of the voices: let the natural pitch finish clearly and let the sharpened pitch carry its own direction, without hammering the clash. What we should hear is the brief crossing of two melodic paths, not a wrong note inserted for effect.

https://www.scielo.br/j/rv/a/v9YDgjn5mz8ZrhPGWMRQrFB/?lang=en
https://www.earlymusicsources.com/youtube/false-relation
https://imslp.org/wiki/Ave_verum_corpus%2C_Bassano_4_(Byrd%2C_William)