He's characterizing the yelling of the two sides like you would normally describe people. "Deep and terrific" is supposed to evoke imagery of a powerful, strong and boisterous man. It's contrasted with "scrawny and faggy", which is supposed to evoke the imagery of a weak, thin wisp of a person.
The "faggy" is defined as you would possibly expect. "Fag", in case you didn't know, is a pejorative term for a gay man, and a common stereotype of gay men (especially during Salinger's time, and ESPECIALLY from the view of Holden Caulfield) is that they are effeminate, wimpy people. So he's saying that the Saxon Hill side sounds like a thin, weak-voiced gay man who could be beaten up by the strong-armed macho on the Pencey side.