NEXT Monday when Carnegie Hall reopens, restored to an earlier glory, the landmark building's newly plastered, freshly painted cream-colored walls can be expected to resound with cheers and bravos. But there will be other cheers as well: cheers of relief from, no pun intended, those unsung heroes and heroines, the occupants of the hall's upstairs studios who have, for over three years, lived and worked through a major restoration. Despite the trials, tribulations, dust, debris and noise, it is unlikely that many inhabitants of the 30 studios (out of a total of 135) used for both living and work space ever seriously considered the possibility of moving anywhere else.

The composer-lyricist Joe Raposo, whose ninth-floor studio was once rented by Eddie Duchin and, later, by his son, Peter, likens the renovation experience to ''having had a studio on the side of Mount St. Helens.'' Yet even when the yellow dust from sanded-down bricks covered the keyboard of his eight-foot Yamaha baby grand or eight tons of rocks were poured on the roof outside, he would gaze out the window toward Central Park and think about the dazzling the view on glittering, snowy nights and of the crackling logs in his oversize fireplace.

Emilia Del Terzo bought a face mask last spring to protect herself from the clouds of dust daily seeping through the Italian wrought-iron gates that front the eighth-floor quarters in which she has resided and taught music for over 30 years. Her space, which she acquired from Pietro Yon, organist at St. Patrick's Cathedral from 1927 to 1943, has oak-paneled walls, a built-in Kilgen organ, a Hammond concert organ (the pipes reach almost to the top of the 24-foot-high ceiling), plus eight adjoining studios with eight Steinways. ''There aren't too many other places where I could have that.''

Then, too, there are the 30-inch-thick walls that enable her ''to play my heart out on the organs at 3 o'clock in the morning.'' For the past year or so Dr. Del Terzo has done a lot of late-night playing: ''During the day, with all those construction workers banging on all those pipes outside my window,'' she says, ''everything sounded like the 'Anvil Chorus.' '' She did welcome the building's new roof (a rubber membrane held down by 100 pounds of rocks per square foot), since leaks from the old one had damaged rare manuscripts, memorabilia, carpeting and costumes (''Have you ever smelled wet lame?'') ''Yes, I cussed a lot during the past year or so,'' she says. ''But no, I wouldn't think of living anywhere else. I remember that when I moved into my first Carnegie studio, I felt like a girl who had been given a doll she'd wanted all her life. I've never stopped feeling that way.'' Among the friends she has entertained and cooked meals for in her small kitchen, she names Bidu Sayao, Licia Albanese, Gabriella Tucci, Roberta Peters and Arturo Toscanini, who fell asleep after a spaghetti dinner. ''He snored,'' Dr. Del Terzo recalls.