From the bottom note upwards, it consists of three perfect fourth intervals followed by a major third interval.

The most common result is a perfect interval, but the range of intervals produced can vary broadly.

These scales split perfect intervals using quarter tones.

Notice that these do not form a perfect interval.

The cadence (or last four measures) uniquely leads to the root by perfect intervals of fourths.

If a perfect interval becomes smaller by a semitone it becomes "diminished"

By definition, the inversion of a perfect interval is also perfect.

Start with the part containing the most notes, the two parts with most perfect intervals, and/or a strong duet quality.

Big was right behind them with a perfect interval.

Similar issues arise with the fifth 3/2, and the minor third 6/5 or any other choice of harmonic series based "perfect" intervals.