Certain sections of the prayer service are commonly sung by the congregation but there are two main ways in which this singing takes place: 1) the Beis Medrash style and 2) the Young Israel style.
In the former, the leader sings a verse and then after him the congregation recites it. Then the leader sings another verse and after him the congregation recites it. Etc. In many synagogues, while the leader is singing everyone sings along without actually saying the words, perhaps with "ay yay yay" and waiting until the congregation’s turn to recite rather than sing the words.
In the Young Israel style, the leader and the congregation all sing the verses together straight through. It is my belief, and for what little a vague second-hand recollection is worth I think I heard that Rav Soloveitchik said similarly, that the Beis Medrash style is what Ashkenazic Jews have traditionally done and the Young Israel style was an intentional break with tradition.
- https://PayPal.Me/lukeisback
"Luke Ford reports all of the 'juicy' quotes, and has been doing it for years." (Marc B. Shapiro)
"This guy knows all the gossip, the ins and outs, the lashon hara of the Orthodox world. He’s an [expert] in... all the inner workings of the Orthodox world." (Rabbi Aaron Rakeffet-Rothkoff)"This generation's Hillel." (Nathan Cofnas)