Daryl Hall and John Oates' Along the Red Ledge and cowrote Earth, Wind and Fire's "After the Love Has Gone." As on Silk Degrees, the arrangements are carefully blocked-out set pieces that boast the precision and texture of big-band charts. In front of these gorgeous backdrops, Scaggs struts his vocal stuff, a white soul man in tie and tails.

Middle man lifts the aura of detachment that's usually surrounded Scaggs. He sings more aggressively than ever, often taking big chances. In the title track, a driving boogie, Scaggs pushes his voice to the manic edge, achieving a thrilling immediacy. Elsewhere, the singer uses his jagged, quavering falsetto not to express tender erotic thrall in the traditional soul manner, but to project the high-voltage carnality of urban life. Middle man could well be Boz Scaggs' response to Donna Summer's Bad Girls, since its milieu is similar: a high-rent, high-rise City of Night where grand passions and cheap thrills are one and the same. Indeed, the cover photo shows a slicked-down Scaggs exhaling cigarette smoke, his head propped on the fish netted thigh of an anonymous showgirl. The artist's air of blithe depravity implies an unabashedly glamorous view of the voluptuary life.

Though the words are hard to understand without a lyric sheet, the song sequencing suggests a hot affair with a hooker. "Jojo," the first number, introduces us to a middle man who could arrange just such an adventure: a gun-toting, mink-clad pimp who gazes down from "dizzy heights" on Broadway's "spinning lights" like a neon Bacchus. The tune's arrangement is a smoother, steamier update of the throbbing pop-disco of Silk Degrees' "Lowdown," the melody a chromatic refinement of Philadelphia International formulas. Middle man's musical style shifts back and forth between this slick, choral pop-soul and the brand of streamlined hard rock that's been a Scaggs signature beginning with "Dinah Flo." As on Silk Degrees, most of the core members of Toto man the hardware. "Breakdown Dead Ahead," the LP's catchiest rocker, is so exhilarating that the romantic smashup it anticipates exudes a deadly allure. This is no warning about life in the fast lane, but an incitement to slam down on the accelerator. "Simone," a slippery-sweet proposition that echoes "My Cherie Amour" and the best of Burt Bacharach, segues into a beautiful ballad, "Y