Why does the Pasuk refer to Miryam as Miryam ha'Nevi'ah?
Rashi: Because she prophesied the birth of Moshe. 1
Rashbam: A prophet is either someone who rebukes or someone who sings praises (of Hashem).
Why is Miryam called the sister of Aharon?
Rashi #1: "Miryam ha'Nevi'ah Achos Aharon" teaches that when she was the sister only of Aharon, before Moshe was born, she prophesied.
Rashi #2: Her name is connected to that of Aharon, who was Moser Nefesh on her behalf when she was later stricken with Tzara'as. 1
Ramban #1: Since Moshe and Miryam are mentioned in the Shirah but not Aharon, the Torah wanted him to be mentioned too, so it called Miryam "Achos Aharon."
Hadar Zekenim (19): It is normal to attribute a woman to the older brother. (It seems that also Rashbam holds like this.)
And it did so in a way that was a Kavod for him, in that he was Miryam's older brother and that Miryam his sister was a prophetess, seeing as he too, was a Navi and a K'dosh Hashem (Ramban).
What are "Tupim u'Mecholos"?
Rashi (in Eruvin, 3b): It means drums and dances.
Targum Onkelos and Targum Yonasan: It means drums and flutes. 1
Why did the women take musical instruments with them into the desert?
The righteous women of that generation took musical instruments out with them in anticipation of the miracles that they were convinced Hakadosh-Baruch-Hu would perform with them.