I am completely unqualified to write about this topic, let's get that out of the way now. However, a potential connection between the Philly soul sound of the 70's and the sound of the Philadelphia Orchestra from the same era feels significant, and it's not something that I can recall reading about in any standard music history accounts.
The Philadelphia International Records label was founded by Kenneth Gamble and Leon Huff in 1971. It was an alternative of sorts (not sure whether it was termed as such at the time) to the Muscle Shoals brand of gritty, blues-heavy soul. The Philly sound was lush, smooth, with complex orchestration and rich string accompaniments. Songs by Harold Melvin and the Blue Notes, Lou Rawls, and Patti LaBelle became massive hits. The O'Jays built an incredible discography, and for my money, stand out as one of the most underrated bands of all time. One can draw a direct line between the Philly groups and the disco music that came to define the 70's.
Somehow, all this great music went underappreciated by the industry at large. Gamble and Huff won their first Grammy in the late 80's -- for Simply Red's cover of "If You Don't Know Me By Now". Today, the Philly sound is rightly revered for the high quality of the music as well as the many innovations made by its creators.
At the same time, the Philadelphia Orchestra had reached its peak under Eugene Ormandy, who served as its musical director from 1936-1980. They made hundreds of recordings together during that time. The orchestra's sound was wholly distinctive, due to its heavy, dramatic string sonority. Ormandy was disliked by classical music critics, for reasons that look embarrassing through modern eyes. He was a tremendous conductor in virtually all sub-fields of orchestral music. Was the Philadelphia Orchestra's sound considered too kitschy, unworthy to be considered amongst the high art of other leading orchestras? The likes of Karajan and Szell were steely traditionalists, proudly carrying the mantle of careful precision and skillful musicianship in the classical music world. The industry marketed their recordings far more aggressively than they did for Ormandy's. The whole "controversy" just feels silly now. Many major orchestras of that era could reach a godlike tier on most nights, and Philadelphia was just as great as any of them.
Philly soul and Philly classical were peaking in the same city at the same time, and their string heavy characteristics sounds were mirror images of each other. This simply can't be a coincidence. And yet I can't find any references to a specific connection between the two, or rock/soul criticism that makes the comparison.
Thom Bell was the main orchestrator and arranger for Philadelphia international. He gave a number of interviews throughout the years. His RnR HOF page notes that he was influenced by Beethoven and Burt Bacharach. He was classically trained and aspired to be a concert pianist. By his own admission, classical music was his life growing up and he knew virtually nothing about pop music through his late teens. Musicians from the Philadelphia Orchestra played the string arrangements on the soul records he worked on. It is inconceivable that he wasn't seeped in the sound of the Philadelphia orchestra by the time he began working with Gamble and Huff. However, I can't find any explicit statement by Huff, Gamble, or Bell about their classical influences. They never claimed to be influenced by Ormandy and the wholly unique Philly classical sound.
The closest thing I could find is Bell's "cheese steak" story. According to him, it's not just that Philly has the best cheese steak sandwiches anywhere in America. More than that, any mom and pop sandwich shop makes a better cheese steak than any restaurant in any city in American could hope to do. Because the cheese steaks, according to Bell, are embedded in the Philadelphia culture in a way that no other city could duplicate. And that's the origin of the Philly sound. It's not taken from a specific time and place, passed linearly from artist A to B. It was sewn into the fabric of the city. One must look at the whole to appreciate the constituent parts. And that whole obviously includes the Philadelphia Orchestra.
