Authentic cadence in music typically refers to a strong, conclusive resolution, and in the context of Roman numerals, it often pertains to the harmonic progressions that lead to such resolutions in tonal music. In Western music theory, authentic cadences generally fall into two categories:
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Perfect Authentic Cadence (PAC): This is usually represented by the progression V-I (dominant to tonic) in root position, with the tonic note (the root of the I chord) also in the highest voice.
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Imperfect Authentic Cadence (IAC): This involves a V-I motion as well but may occur in inverted positions or with the tonic note not in the highest voice.
Here’s how you might see these cadences represented with Roman numerals in a major key (e.g., C major):
- PAC in C Major: V (G) - I (C)
- IAC in C Major: V (G) - I (C) but could be G/B (first inversion of the V chord) - C (or C/E).
In minor keys, the harmonic function remains the same, but the chords will be represented accordingly. For example, in A minor:
- PAC in A Minor: V (E) - i (A)
- IAC in A Minor: V (E) - i (A) but could also involve some inversion like E/G# - A.
In summary, the codified movement of chords using Roman numerals helps illustrate the relationship and function of the chords within the key, particularly as they relate to authentic cadences.