Harrison Ridley Jr., 70, Philadelphia's sagacious jazz musicologist and radio host who expressed approval for a song with his on-air trademark "Yes, indeedy," died Thursday of complications of a stroke.

Mr. Ridley, who was born and raised in West Philadelphia, educated and entertained jazz devotees listening to Temple University radio on Sunday nights. A proud and discriminating collector of jazz, Mr. Ridley often played songs from his personal collection of more than 8,000 recordings (most of them vinyl) and books, and shared his vast knowledge of the history of jazz.

Mr. Ridley's radio program, The Historical Approach to the Positive Music, won many awards and was a mainstay of WRTI-FM (90.1) programming. His soft, gentle baritone - with never a hint of intellectual arrogance - was on every Sunday from 8 p.m. to midnight. He was proud that he never missed a program until he slipped and fell during the blizzard of 1996.

The humble keeper of jazz history worked as a custodian for the Philadelphia school district for 39 years, and was a DJ at WRTI for 32. His was the longest-running program in the history of the station.

Mr. Ridley taught jazz courses at Temple and at Villanova University, was a consultant to the Library of Congress, and used his personal collection to clear up historical misconceptions on the air and in the classroom.

He documented the majesty of jazz, which he considered America's classical music. At the time of his death, he was writing two books on jazz - one on Duke Ellington and one on the history of jazz in Philadelphia.

Mr. Ridley said in a 1996 Inquirer interview that he never owned a car, eschewed red meat, and did not smoke or drink. The gentle giant was a familiar sight on subways and buses, usually toting a cloth bag filled with albums and books. Each morning, he planned his lectures and radio topics, and meditated.

"I always tell students, 'Love yourself - you create a halo. People will be drawn to you,' " Mr. Ridley said in 1996. He lived in West Philadelphia with his wife and daughter.

"I miss Harrison already," said Maureen Malloy, WRTI's jazz director. "Harrison Ridley Jr. is one of the reasons I fell in love with jazz."

Mr. Ridley tried to play the xylophone and the vibes when he was a child, but neither stuck. He was not an expert on music theory, but was a maestro of jazz history.

The first record he bought was a 78 r.p.m. of Lionel Hampton playing "Flying Home," he said. But Mr. Ridley specialized in the history of Duke Ellington. He owned more than 600 Ellington records and 70 CDs, his largest trove by a single artist. He saw Ellington perform more than 30 times.

After graduating from West Philadelphia High School, where one of his classmates was pianist McCoy Tyner, Mr. Ridley joined the Army. He spent most of his pay on records.

After he was discharged in 1964, he attended every jazz concert he could. He witnessed saxophonist and flautist Yusef Lateef record his Live at Pep's LP in 1964 at the jazz club at Broad and South Streets, Pep's Musical Bar.

In 1975, Mr. Ridley was asked by then-WRTI music director Buddy Cohen to do on-air commentary during a 12-hour Ellington marathon. Mr. Ridley and Cohen had met in a record store while scouring bins. Mr. Ridley carried 200 records to the studio, and worked all 12 hours. Listeners requested Mr. Ridley to chat about jazz history, and in 1976, the show was his.

Mr. Ridley was not a critic. His show was a draw for musicians when they passed through Philadelphia. Mercer Ellington, Art Farmer, Jimmy Heath, Max Roach, and others sat behind the WRTI microphone with Mr. Ridley and talked about jazz. Mr. Ridley seemed to know as much about the artists' music as they did.

Mr. Ridley recognized rising young talent on his show. And he often focused on arrangers and women artists who were not getting what he considered deserved publicity. He featured pianist Mary Lou Williams, even after her death in 1981, on the first Sunday of every year because "she's still dramatically underrated."

"I remember Harrison's broad and authentic smile with which he would greet me, along with the occasional bear hug," said David S. Conant, WRTI's general manager. "Knowledgeable, and sincere in his love of jazz, he was above all a gentleman and a truly gentle man."

"Harrison was so quiet, but he had so much in him. He kept pouring it out . . . just like a great jazz musician," WRTI colleague Bob Perkins said. "He never repeated himself. He played it differently every time."

Mr. Ridley is survived by his wife, Janet; a daughter, Jade Wideman-Ridley; and a stepson, Laurence E. White Jr. Plans for a funeral have not been announced.

Contact staff writer Gayle Ronan Sims at 215-854-4185 or gsims@phillynews.com.