The Mellon Jazz Festival doesn't start until next Friday, but the bank people are staging a free outdoor jazz concert as a prelude today from noon-2 p.m. at their Broad and Chestnut bank building. Mike Pedicin Jr., a saxophonist who has played with Dave Brubeck and now leads the orchestra at the Atlantis Casino in Atlantic City, leads a jazz quartet at the lunchtime concert. Info: 553-3000.
The Delaware will look its best Saturday at 11 a.m. when some 60 gracefully beautiful sailboats glide off for the start of the Moshulu Cup Race from the Moshulu Restaurant, located on a ship anchored at Penn's Landing. The craft in the race will sail to the Walt Whitman Bridge, and back - some six miles. If you have a boat, you can still register for the race by calling 609-966-1352. Other info: 925-3237.
Joe Frazier and Larry Holmes take part in the "Battle of Singing Heavyweights" Saturday night at 10 at the Sands Casino in Atlantic City. But the former boxing champs won't be swinging at each other. They'll be vocalizing with their respective groups. You can see the retired Pennsylvania pugilists for $15 a ticket. Info: 609-441-4000.
The Penn's Landing Great Plaza goes Greek Saturday and Sunday from noon-7 p.m. for the annual Hellenic Festival. You can enjoy Greek music and dancing while wolfing down delicious souvlaki, gyros and other classic Hellenic food. And you can choose from a selection of arts and crafts. No admission charge. Info: 923-8181.
If you're planning a June wedding, you can get some tips on how to do it ethnically at a new Balch Institute exhibition opening Monday called ''Something Old, Somethng New: Ethnic Weddings in America." In addition to 75 photos of weddings in which the couples used rituals and customs from their foreign heritage, wedding artifacts and costumes are on display at the museum on 7th Street, south of Market. Exhibited are African wedding clothing, a Welsh love spoon, Ukrainian wedding bread, and a sequined East Indian sari. The exhbition runs through Nov. 28. No admission charge. Info: 925-8090.
Israeli-born violinist Itzhak Perlman, a onetime boy wonder who appeared twice at 13 on the old Ed Sullivan TV show in 1958, solos with the Philadelphia Orchestra Tuesday night at 8 at Mann Music Center, 52nd and Parkside. He'll play Mendelssohn's Concerto No. 2 in E Minor. Tickets are available by coupon published in Daily News. Limited number of other free tickets at box office night of performance. Info: 878-7707.
Soupy Sales, the slapstick comic who holds the world's record for receiving pies in the face, comes to the Comedy Factory Outlet Wednesday night for 8 and 10:30 p.m. shows. He was a big man on TV and radio in the 1960s with his White Fang, Black Tooth, Pookie and Hippie. Quite a switch for a guy who started his show biz career as a radio jazz DJ. Tickets are $11. Info: FUNNY- 11.
Art Blakey, born 68 years ago in Pittsburgh, is still banging the drums as if they're going out of style. We'll be able to catch his explosive work with his Jazz Messengers Wednesday night at 8 and 10 p.m. at the city's newest jazz room - Memphis, at 2121 Arch Street (formerly the site of the old Just Jazz). Tickets are $12. Info: 569-1123.
The world premiere of Louis Lippa's "The Stone House" is being held at the Second Stage of the People's Light and Theatre Company, in Malvern at 39 Conestoga Road (Route 401 between Routes 30 and 202). The drama is set in a Philadelphia rowhouse in 1937. Tom Teti, a regular with the company, stars as a husband and father who struggles between his desire to fight for the Socialist cause in the Spanish Civil War - and his loyalty and devotion to his wife and retarded daughter. It previews Wednesday and Thursday, and opens next Friday. It runs through Aug. 2. Tickets are $10 for previews; $14.50 and $18 for regular performances. Info: 644-3500.