NEW YORK'S NEWEST

When feeling tuneful about spring fashion, American style, the lyric to sing is "There'll Be Some Changes Made." Signs that hemlines are on the rise, pants are becoming roomier, and waistlines are roaming around were impossible to ignore at early showings on Seventh Avenue and during later national press weeks.

Still, any flat-out pronouncements on matters like skirt lengths and waistlines would be risky.

It is true that shapes have been loosened up to a degree, so it is quite all right to state categorically that lines are not so strict. But certain basic style information cannot be pinned down precisely. The measurements of skirts and the location of waists are not among next season's fashion constants. They are peregrinating factors.

The broad squared-off shoulders that have yet to gain general acceptance are still wide. But they have been rounded out, so perhaps women will like them better now. The softer curved shoulder makes the wedge or inverted V a shape of the past.

Sleeves are big and full -- puffed, pleated at the shoulder, or gathered into leg o'muttons. Skirts are less straight and narrow. Jackets are both longer (hip length) and shorter (brief bolero or midriff types).

It could be said that skirts are undeniably shorter (it could, that is, if we were always dealing with hems that are on the level). But when someone like Halston hedges around with skirts that expose the knee in front and dip to mid-calf length in back, who's to be pinned down?

Aside from Perry Ellis, who showed ultrashort little circle or pleated skirts with his play clothes, few New York designers flirted with the idea of a return to mini-land. And even Ellis places some of his hems far below the knee as proof that skirt lengths are current fashion variables.

The majority of designers are easing away from long, plumb-line skirts with slits. The move is toward flared, lightly gathered, or kick-pleated styles that hover around knee length.

Changes in pants styles is another area where Ellis is in the forefront. The baggy jean, which originated in Europe and is having a runaway vogue with trendy types in New York, is fast putting skin-fit styles on the fashion shelf, and baggies have strongly influenced trouser looks for spring and summer.

The Ellis pants are deeply pleated at the waist or are gathered at yoke tops, and some are as full as Hans Brinker's in "The Silver Skates." The length (most of Ellis's trousers are chopped off below the calf of the leg) heightens the Dutch look.

Other designers liked wider, shorter pants, too. Capri, clam- digger, and Bermuda styles with knee socks and tie oxfords turned up on a number of runways. Many designers presented citified shorts with matching jackets as a warm weather change-off from suits.

"Whither the waistline?" -- another undetermined spring question -- remains moot. Nipped-in jackets with minuscule peplums are as valid as nonwaisted chemise dresses. The dropped torso style (where the beltline encircles the hipline) cropped up at several houses. The Anne Klein collection is full of flapper dresses that break into flounces or box pleats below low beltlines.

Speaking of flounces, New York was as enamored of ruffles as Europe was. Ruffle-skirted dance dresses at Oscar de la Renta and Bill Blass are as short as a ballerina's tutu.The knee-baring dress with the flip little skirt is outdating long evening styles. Several houses showed only a few long dresses for next season.

While changes are in prospect, there are certain continuing trends: divisions of two and three colors, asymmetry, and geometric cuts; lace-trims and Edwardian looks; baby-collared shirts with country club classics; handmade knits of cotton boucle in abstract patterns. They provide continuity to the course of current fashion.