what is half cadence
If the melody accompanying this harmonic progression arrives on do, it is called a perfect authentic cadence; it the melody ends on mi or me (or more rarely sol), it is called an imperfect authentic cadence. Phrases that end on V without progressing to I are called half cadences. These cadences typically contain re in the melody, though ti and sol are also possible points of melodic arrival. The V is almost invariably a triad, rather than a seventh chord, and it is always in root position (D5).