Conversation so far:
What was their style of sound?
punk-inflected hard-rock.
Did their style change over time?
songs got slower.
Did their music sound differently from getting slower?
Hook's bass carried the melody, Bernard Sumner's guitar left gaps rather than filling up the group's sound.
Was the sound of their music inspired by anything?
inspired by its energy.

Question: Was the vocal sound of the band similar to another singer or group?
Self-contained rewrite: Besides it's inspiration, was the vocal sound of Joy Division similar to another singer or group?