AND WAIT, THERE'S MORE: Dave Mason has an old pal helping out on his new album--Steve Winwood, who hasn't worked with his ex-Traffic partner in 15 years. Winwood contributes some keyboard work to Mason's upcoming "Two Hearts" album, which is due out in September from Voyager Records. . . . Our Rock Stunt of the Week goes to Capitol Records, which is releasing "Jam Tonight," yet another new single from Freddie Jackson's long-running "Just Like the First Time" album. To grab some attention, the Capitol promo wizards are due to send out jars of strawberry jam to radio programmers and retail outlets, with Top 40 deejays getting Freddie's "Serious Cross-Over Jam" and black jocks receiving Freddie's "Down Home Tasty Jam." . . . Now that you've digested that, how about saying (real fast): French, Frith, Kaiser & Thompson. A perfect name for a law firm, right? Actually it's a new quartet made up of several founding fathers of progressive rock, including Captain Beefheart veteran John French, Henry Cow's Fred Frith and ex-Fairport Convention leader Richard Thompson, who's gone on to build a loyal following as a solo artist in recent years. The Not-Quite-Superstar group's new album, "Live, Love, Larf and Loaf," is just out from Rhino Records, featuring such originals as "Wings a la Mode," "Killerman Gold Posse," "Drowned Dog Black Night" and a bizarre cover version of "Surfin' U.S.A."