How did Miriam sing with men present - it's kol isha??
Many answers are given. One is that since the Divine Presence dwelt among the Jewish people her voice didn't pose a problem because it wouldn't lead to improper thoughts. The Holy Bnei Yisaschar takes this one step further and explains the pasuk in Yeshayahu [12/6] צהלי ורוני יושבת ציון - Sing women of Zion! But what about kol isha? The pasuk continues כי גדול בקרבך קדוש ישראל - Hakadosh Baruch Hu is among you [so there is no concern for improper thoughts].
I add my two cents [the finances are tight these days:-)] - If a person walks around thinking about Hashem and holy things the Shechina will dwell upon him and he won't be negatively affected by his surroundings.
