The show debuted on a handful of station in April of 1927 WJZ, WBZ, WBZA, and KDKA. the big launch was in July that year. Philcoradio.com summarizes it nicely so I'll just quote them:
"On July 20, 1927, Philco’s manager of sales promotion, Sayre M. Ramsdell, sent out a letter to Philco’s dealers informing them of a new weekly broadcast to begin on Friday, September 16th.7 Called the “Philco Hour,” the program featured nationally known soprano Jessica Dragonette, and the Philco Orchestra conducted by Harold Sanford. Henry M. Neely, otherwise known as “Philco’s Old Stager,” served as host of the weekly broadcast, which was carried initially over 26 stations, scattered across the country, on the NBC radio network."In 1929 Philco began sponsoring broadcasts of the Philadelphia Orchestra conducted by Leopold Stokowski.It was later they would move on to the Paul Whiteman Orchestra.
Starting in 1930 Philco cut ties with NBC. They were no longer on the Blue network. Philco syndicated the program on about 50 stations via transcription discs. That started with an initial batch of eleven half-hour programs. Each disc only held 10 minutes of audio so it took 6 twelve-inch discs to make one whole show. (Remember this was all at 78 rpm.) This is all interesting because symphony Orchestras had been on the wane since about 1930. This is at least partly due to the great depression. The book "America's Symphony Orchestras and How They Are Supported" by Margaret Grant pointed this out succinctly"
Shortly thereafter Philco launched another Tuesday night program which was carried by CBS. That might have been specifically to antagonize NBC who's own orchestral program was now had direct coast-to-coast competition. In 1946 Skitch Henderson became the musical director. That same year Bing Crosby became the new host replacing Henry Neely. The program was still being syndicated on transcription discs. The moved to Ampex tapes in late late 1940s. I lose track of the program there. I know they were airing the Philco Hour on TV by 1952. But I cant seem to close that gap."The use of symphony orchestras by radio advertisers declined following 1930 when broadcasting began to be employed less as a good-will medium and more of a direct sales stimulus. however, some of the outstanding sponsored hours, including the Philco, General Motors and Ford programs gained their greatest audiences after this time."