What is the meaning of "v'Yisedu"?
Rashi: The workers founded the foundation of Heichal Hashem.
Were the Kohanim dressed in trumpets?!
Rashi: They were dressed in Bigdei Kavod (Ibn Ezra - Bigdei Kehunah 1 ), and held trumpets in their hands, to blow them 2 .
Malbim: Rashi holds like the Rambam (Hilchos Klei ha'Mikdash Perek 8), that Kohanim may wear Bigdei Kehunah only at the time of Avodah. The Ra'avad disagrees; he can say that they wore Bigdei Kehunah (like Ibn Ezra says). Even the Rambam could hold that they wore Bigdei Kehunah for Avodas ha'Tamid, and they may continue to wear them the entire day.
Malbim: Kohanim blow trumpets only on Mo'adim (Rambam Hilchos Klei ha'Mikdash Perek 3); it was a Hora'as Sha'ah to consider this a Mo'ed, due to the great Simchah.
What are "Metziltayim"?
Rashi: They are musical instruments, like "Tziltzelei Shama."
What was "Al Yedei David"?
Rashi: They sang songs of David.
Ibn Ezra: Because one plays instruments with the hand, the song is called Yad.
