Sometimes, to heighten interest, a composer will signal the imminent arrival of a cadence, but at the last minute withhold either melodic or harmonic closure, thus necessitating a continuation of the phrase.
The most common form of deceptive cadence substitutes ^5 - ^6 for the bass ^5 - ^1 pattern, usually while retaining stepwise moton to the tonic in the soprano voice. The result is a V - vi progression in major keys, a V - VI progression in minor:
Often a IV6 is used in place of vi:
By using mixture, an especially dramatic effect is achieved:
Deceptive cadences, however, are not true cadenced at all, but simply devices for postponing an authentic cadence. Historically, composers have made use of a wide variety of ways for doing so in addition to the classically deceptive formulas shown above.
Two examples of avoided cadences are given below:
And here, Mozart's substitution of applied vii7 for the anticipated goal tonic creates a deceptive effect.
