Piccardy third
An example of mode mixture, the picardy third (Tierce de Picardie) is a raised third in the final tonic chord of a composition in minor, the use of which originated in the 16th century and the Baroque era. It makes the final chord a major triad rather than the expected minor triad of the natural, melodic, and harmonic minor scales.
The interval strength, or lowest possible location in the harmonic series, and thus consonance and "stability", of minor triads is less than that of major, which interprets major as more "stable", a major triad being found in the 4th, 5th, and 6th harmonics of a pitch, while the minor being the 5th, 6th, and 7th. This may explain the picardy third, since it would be more strong and stable, and thus conclusive. Also supporting this, the picardy third is still considered part of an authentic cadence, the strongest cadence.
