WHEN YOU CONSIDER how (blessedly) restricted the commercial areas of the Massachusetts Avenue/MacArthur Boulevard corridor are, it's an even more pleasant surprise that the few restaurants and bars in that neighborhood are so attractive. (Yes, every once in a while we miss Trav's, but only when we're in the mood to play cycle-seat roulette.)

One of the newest, and almost certainly least visible, additions to the area is Concepts Restaurant in the "English basement" level of Little Falls Mall on Sangamore Road in Glen Echo (301/229-0900), which has at least four things going for it: plenty of free parking; an unusual but not alarmingly inventive menu, despite the name; extremely reasonable prices; and the deft piano of Peter Robinson.

Robinson, who was a longtime fixture at the Old Ebbitt Grill's Atrium downtown, was beginning to feel the weight of beetling glares from late-working lawyers overhead. (Although if even they found his embracing style distracting, that's a commendation in itself.) In any case, he has wandered into the Concepts partnership and supplies the entertainment Wednesday through Saturday from about 6:30 on. It's primarily instrumental, though he does sing a little; and it adds a soothing, easy dimension to dinner. In fact, really appetizing dinner music is so rare these days that you scarcely notice until you actually hear some again. Even better, you can graze through a rendezvous and barely blush at the tab.

The restaurant is only two smallish rooms right now, with an old-fashioned stool bar; but Concepts will eventually move into larger quarters in the mall when it's renovated. The nibblies are generous: spicy ginger and peanut noodles, "the best chicken liver pa~te'" that may well live up to its billing, blue and white corn nachos and a combination platter -- marinated veggies, the noodles, feta, pa~te', chorizo and shrimp -- that at $6.95 is meal aplenty. For bouillabaisse fans who can't wait for Fridays, there's a small tureen on the regular menu for $4.25. Personally, we demolished the sage pasta with sun-dried tomatoes, basil, goat cheese and calamata olives -- all we could eat at $4.95.

The only shortfall at the moment is the beer and wine list: no locals, and the only champagne available was Dom Perignon. But more variety, and less expensive labels, are in the works.

ALL THAT JAZZ: The fourth annual Thelonious Monk Institute of Jazz Instrumental Competition returns to the Smithsonian's Baird Auditorium Saturday and Sunday, but this time with a twist: Instead of featuring pianists, as in previous years, this year's competition salutes Louis Armstrong and features 20 young jazz trumpet players from Poland, the Soviet Union, Canada and Argentina as well as the United States. The shift from keys to valves is the first modulation in the institute's program; and the judges -- Nat Adderley, Clark Terry, Donald Byrd, Red Rodney and Snooky Young -- are as solid as the cash awards, ranging up to $10,000.

The quality of the competition has been remarkably high. The first year's winner was the fluid Marcus Roberts, whose debut album was a No. 1 bestseller, and Joey DeFrancesco, a finalist in the 1987 round, was signed on the spot; DeFrancesco will perform Sunday while the judges make their final decision.

The Monk Institute is a nonprofit educational organization with mostly corporate support (notably Absolut and Ford). Tickets to Saturday's rounds, starting at 1, are $5 (free to Resident Associates, Beethoven Society members and students with ID). Tickets to Sunday's finals at 3:30 are $12 ($10 members, $8 students); 202/357-3030.

ALL THAT JAZZ, 2: Two long years after leaving Old Town for Tenleytown, Cates Jazz Club is fully liquor-licensed and unrolling the red carpet for hometown favorite Shirley Horn, just back from Europe and performing through the weekend ($14.50 Friday and Saturday, $8.50 Sunday; 202/363-2600). She'll be followed by Jamie Broumas, whose quartet will be the Tuesday house band.

At the same time, Cates unveils a new acoustic blues-only showcase called the Chicago Room, decorated in Windy City memorabilia (not a comment on the entertainment, one assumes) and sporting a non-Washingtonian cover of only $3. Archie Edwards opens the light-fare room, playing Fridays and Saturdays through the month.

Speaking of Horn, hometown fans should catch the Peter Falk movie "Tune in Tomorrow" to see her singing "I Can't Get Started" with Wynton Marsalis's backing. Her "You Won't Forget Me" album, featuring Wynton and Branford Marsalis, Miles Davis and local stalwart Buck Hill, among others, will be released after the first of the year.

For more jazz options this week, see The Doctor's Bag.

CARPENTER CALENDER: Yes, Mary-Chapin Carpenter is playing three nights at the Birchmere next week; and no, you can't go. Carpenter's Thanksgiving homecoming shows are already sold out, but you can see her and the band in New York, TV-style -- Friday night on the David Letterman show and Monday on "CBS This Morning."

Carpenter is riding a PR wave these days that started with the standing ovation she received from the star-spangled Opry crowd at the Country Music Awards show last month. Her new album, "Shooting Straight at the Dark," looks like the crossover she's been waiting for, moving on both Billboard's country (26 with a bullet) and pop (166) charts; she's profiled in Elle, raved up in People and after a week's rest here, she picks up the West Coast half of her tour, including a showcase at the Roxy in L.A.

Incidentally, local picker groupies may be interested to know that the peripatetic Jon Carroll has rejoined the band on keyboards, re-subbing for the booked-to-the-ears Peter Bonta, who's producing up a storm at Wally Cleaver's studio.

TEASER TIME: The Dec. 10 "mystery concert" WHFS has been hinting at marks the beginning of the giving season -- in this case, coats for disadvantaged kids. The DAR Constitution Hall date features John Hiatt, Shawn Colvin and Lowen & Navarro; and although tickets are $19.91 (saluting the station's 99.1 dial spot), those patrons who bring new or good used coats or jackets with them are eligible for special giveaways. Tickets go on sale today at Ticketron (800/543-3041). Remember, a lot of teenagers come in adult sizes, so just because you don't have children doesn't mean you can't chip in.