1)
What is the meaning of "Tzahali"?
1.
Radak: Raise your voice in song and praise of Kel.
2)
Should only residents of Tziyon sing?
1.
Malbim: Especially they should sing.
3)
Why does it say "Gadol b'Kirbech Kedosh Yisrael"?
1.
Radak: His name is great amidst you with wonders that He did, like it says in the Nevu'ah of Gog and Magog in Yechezkel (38:23) "v'Hisgadalti v'Hiskadashti