What does this Mizmor discuss?
Radak #1: Some say that David said it when he was exiled among Pelishtim.
Radak (2) #2: Some say that it refers to people in this exile; this is correct. It is in the singular, as if each person screams from Galgal (the spherical shell that houses the Heavenly bodies), that the honor should return to Eretz ha'Kodesh.
Malbim: It refers to Galus; it has three parts 1 . In Galus, we lack two esteemed matters. (a) Giluy Shechinah and Nevu'ah. (b) Miracles - "Ososeinu Lo Ra'inu Ein Od Navi" (74:9). Before, we had them - "ha'Shama Am Kol Elokim Medaber mi'Toch ha'Esh Kasher Shamata Atah va'Yechi;
He later says that the third part is Mizmor 43.
Who are Bnei Korach who composed this Mizmor?
Rashi: Asir, Elkanah and Avi'asaf 1 (Shemos 6:24).
Radak (2) #1: Some say that it is one of the three Bnei Korach 2 .
Radak (2) #2: Some say that it was a son of Heiman, the grandson of Shmuel ha'Navi 3 .
Radak (2) #3: David composed it with Ru'ach ha'Kodesh; he gave it to singers 4 descended from Korach, in David's time, to sing them. Because Bnei Korach were Nevi'im, their descendants are attributed to them.
How were Bnei Korach able to compose (or sing) Mizmorim? Everyone connected to Korach was swallowed in the ground (Bamidbar 16:32)!
Rashi (from Shocher Tov): Initially they were part of their father's counsel, but at the time of the rebellion they separated. When the earth's mouth opened, and everything around [Korach, Dasan and Aviram] was swallowed, their location remained intact inside the mouth of the earth - "u'Vnei Korach Lo Mesu" (Bamidbar 26:11) 1 . There they sang Shirah, and composed these Mizmorim (42-49). They rose from there, and Ru'ach ha'Kodesh rested upon them. They prophesied about the Galus, Churban Beis ha'Mikdash and Malchus Beis David.
Bartenura (26:11): They were punished to dwell alone Midah k'Neged Midah, for they were in the feud, and cause others to separate one from another. (This is like Chilul Hashem, for which Teshuvah, Yom Kipur and afflictions do not atone (Yuma 86b), for he caused others to sin.- PF)