What is "Mesos Libenu" that ceased?
Ibn Ezra: Korbanos.
Palgei Mayim: From when Leviyim ceased from the gates and from singing (14), our joy ceases, for "Naflah Ateres Roshenu" (16).
What are "Mecholenu"?
Ibn Ezra: Those who sing. 1
Mechilta and other Midrashim on Shemos 15:20: "Uvi'Mcholos" are musical instruments 2 . Perhaps the same applies here. (PF)
It seems that this refers to Leviyim, who sing while Korbanos are offered. (PF)
Some say that they are dances, and so implies Rashi. Ta'anis 31a - in the future, Hashem will make a Mechol (dance in a circle) for Tzadikim. Perhaps also here it refers to dancing. However, it is better to say that they are instruments, which are used also for eulogies (Rashi Kesuvos 46b. We do not bring flutes to Beis ha'Evel on Chol ha'Mo'ed (Tosefta Mo'ed Katan 2:9), i.e. but people did so not during the Mo'ed!) (PF)
