Final answer:
A perfect fifth below B-flat is E.
Step-by-step explanation:
In music theory, a perfect fifth refers to an interval consisting of seven semitones, or half steps. To find a perfect fifth below B-flat, we need to count down seven semitones. Starting with B-flat, we count down by half steps: B-flat -> A -> A-flat -> G -> G-flat -> F -> E.
Therefore, a perfect fifth below B-flat is E.
It is important to note that in music, intervals can be described in terms of both the number of letter names and the number of semitones. For example, a perfect fifth can also be described as a distance of five letter names (B -> A -> G -> F -> E). Nonetheless, the corresponding number of semitones remains constant.