What is the meaning of "Yis'u [Midbar v'Arav]"?
Rashi: Raise your voice in song.
Radak: This is a metaphor, as if the Midbar and cities will sing loudly. Some places in the Midbar have cities.
Malbim: Cities in the Midbar, separated from civilization, will begin to sing.
What is the meaning of "Chatzerim Teshev Kedar"?
Rashi: [People of] Midbar Kedar - now they live in tents. They will raise their voices and sing. There will be cities and Chatzerim fixed there.
Radak: Bnei Kedar live in tents in the Midbar. They are like Chatzerim, i.e. villages - "u'Vatei ha'Chatzerim" (Vayikra 25:31). They do not dwell together; they are scattered in the Midbar, like open cities. It says Teshev (singular) regarding the congregation of Kedar, like "va'Tehi Yisrael", "va'Tehi Aram" (Shmuel II, 24:9, 8:6). The verse mentions the Midbar and Bnei Kedar, for Yisrael will leave Galus via the Midbar.
Malbim: Also Kedarim who live in open Chatzerim that are not cities, will sing.
Who are "Yoshevei Sela"?
Rashi citing Targum Yonasan: They are the dead, who [now dwell in rock, and] they will be revived.
Radak: They are people in towers built on rocks and mountains. They see the Midbar and Aravah from afar.
Malbim: They are individuals who dwell alone on mountains. They will scream to those who dwell below, and tell them the wonder.
