It's actually そう、街角ではだれもが急いでた, and そう means "yes/certainly/exactly/surely". The main purpose to insert そう there is to fit to the rhythm/melody in that case, as is often the case with lyrics.
examples (all from lyrics)
色とりどりの優しさが今ではそう何よりの宝物だよ
適度に気楽に手を抜こう
心の中まではそうしばれやしない
君なしではそう水に浮いた葉の船の用
そうまるであの頃と何も変わらない
まるで全てがそうまるで何もかも全てのことが上手くいっているかのように見えるよね
やばいと感じた本能的に繰り返すそうまるで媚薬のようで深く深くはまってく濡れたその唇に
(The last two lines are good examples that how not-so-important phrases are inserted or how irregularly the word order is twisted for the rhythm/melody in lyrics, in other words, how inappropriate lyrics are as a material of learning Japanese especially for beginners.)