1)
Why does the Pasuk add the prefix 'Hey' to the word "ha'Kohanim"?
1.
Targum Yonasan: To teach us that only Kohanim who do not have a Mum are eligible to blow the trumpets.
2)
What are the ramifications of the Pasuk "u'Venei Aharon ha'Kohanim Yisk'u ba'Chatzatzros"?
1.
Rashi (in Divrei Hayamim 2, 6:7 & 29:26): Even though the Levi'im blew the other instruments in the Beis-Hamikdash, it was the Kohanim who blew the trumpets.
