FALL fASHION. This year's collections sport lavish touches, but simplicity and an overall mood of restraint prevail

AMERICAN designers are proposing uncluttered, sleek, no-frills dressing for fall. But no-frills, as they see it, does not mean Spartan or boring. Today's clothes should be uncomplicated enough to meet modern requirements, but, besides being easy to wear, they must be a pleasure to the eye, a treat to the senses. With that end in view, influential designers who presented new fashions here during the big second week of openings explored a range of styles. There were hooded ethnic-inspired pictorial sweaters at Adrienne Vittadini, soutache-embroidered suits at Mary McFadden, and snappy black dinner dresses in the new United States collection of Karl Lagerfeld, among other offerings. But the fluffy-ruffle school was nowhere to be seen; the gussied-up look was avoided. Instead, designers concentrated on juxtapositions of beautiful fabrics and textures that give the simplest combinations a feeling of subtle elegance.

Solid colorings -- darks, lights, or brights -- predominate. They are enriched with paisleys, velvets, tapestries, and plaids as well as flowered and otherwise patterned knits. But despite such lavish touches as opulent fur trims and helpings of flash and glitter now and then, a mood of restraint prevails. It is often leavened by romantic overtones.

The dandified air of Ralph Lauren's new collection is a case in point. Liberal use of velvet -- wine, brown, and black, primarily -- extends from day through evening, in trousers, long skirts, vests, jackets, dresses, greatcoats, and opera capes. Mixed in with the velvets: giant tartans, tweeds, suedes, and rose-patterned tapestries for a total effect that is beguiling.

The tapestry idea carries into sweaters, too: flowered jet-buttoned cardigans and intarsia-knit pullovers. Lauren's cashmere dresses and tailored velvets are often unadorned. Other times, he adds nostalgic notes -- lace fichus, delicate organdy blouses with ruff necks, Edwardian watch fobs, and pearl chokers -- as softening touches.

In the wake of current interest in India and the British Raj, a passion for paisley has taken hold in fashion. At Gloria Sachs, short or nipped-in longer jackets and midcalf challis skirts play off large-scaled paisleys with plaid. Many of her prints have rose-printed borders integrated into the plaid or paisley. There are shawls and stoles of these patterns-on-patterns, as well as a quilted sable-edge coat and a similar jacket of paisley. It is sportswear with a high degree of finesse.

Calvin Klein's way with paisley is less pervasive, but he takes it into the modern age, too: with his group of silk paisley shawl-collared lounging jackets over gray flannel pants, for instance. There are silk blouses and long, high-waisted, flared challis skirts of paisley combined with cavalry twill, tweed, or velvet.

Perry Ellis has sweaters inlaid with motifs from the Unicorn Tapestry, and commedia dell'arte-patterned jerseys. Ellis favored minis with matching tights -- but Klein, Sachs, and Lauren kept skirts at midcalf or longer. This was a welcome respite from the outbreak of itty-bitty short skirts that took over Seventh Avenue during the previous week's shows.

Nearly everything at Calvin Klein except the cropped jackets is belted with a two-inch-wide cinch. Almost all coats (they are long and roomy) are double-breasted. New sweaters have fur collars. Even better perhaps is the untrimmed cable-stitched camel cardigan. It's loose in shape and finger-tip length, worn with an ivory silk shirt and honey-color twill pants. Distinctions between day and evening clothes are lightly drawn here. Calvin Klein's fashions are of a quality that goes from working hours to dinner and after, with different blouse, a change of shoes, and a little jewelry added.

Day and night are a lot more clearly defined at Bill Blass and Oscar de la Renta. Both these designers pull out all the stops for their big-bankroll clienteles, who prefer dressing up to dressing down. Covetable day clothes at Blass include the paisley wool suit; a good many jersey dresses, some of which have hip bands of contrasting color, others, siren-like draping; and ensembles of big buffalo plaids with smaller renditions, too (the buffalo plaid is similar to checks and reminiscent of Adirondacks logger jackets).

The sound track at Blass played ``Money Isn't Everything,'' but his evening clothes said maybe it is. Huge cabbage rose prints in offbeat colorings, printed panne velvets, and cut velours in slinky shapes filled the runway. There were cashmere bathrobe coats over cashmere pants and jacquard shirts, clingy laces in fire red, and black velvets with enormous diamant'e buttons.

De la Renta's appealing collection has buffalo plaids, too. Also hip-swathed two-piece cashmere dresses, tapestry wool cardigans, paisley blouses, and wonderful quilted silk jackets and coats. Shoulders are big and lengths varied, although just-over-the-knee is his preference. Black velvet and brilliants trim the lemon, mint, and hot pink late-day turnouts. Variations on the hot pink of India are in fact the point of departure for a splendorous display of Raj finery: slender printed chiffons, hammered satins, and flocked satins, decked with a maharani's ransom of rubies and emeralds -- albeit fake, in this case.

Possibly not the no-frills approach. Nevertheless, these two pets of the private-jet set have given up on the elaborate bouffant gown. Now it's the svelte sheath dress that's the way to go to the charity ball.