Leeder -

Your dad was probably "right," and everybody else was tuning a semitone low - but the real question is "what was everybody else tuning to?"

I played sax and clarinet in a small combo for a while in the 50s, mostly at local "Legion Hall" dance venues. All of our instruments were built to what we called "concert pitch" at A440 Hz. We never found a place to play that had a piano tuned at "concert." I'm not sure it would be safe to say that they were all tuned the same, but it was common to tune them at - least approximately - to what was then called "standard pitch" at A400 Hz.

The only one in the band who could really get in tune with those pianos was the drummer. The 'bone player could adjust his slide postitions "by ear," so he could get by. Our trumpet (actually a Bb cornet) had an "A slide" that he inherited from his dad, who had played a lot in the 30s, so he could make an "instant swap" to something a lot closer. By the time I'd pull the mouthpiece on the sax out far enough to get close - the mouthpiece would fall off.

By the 30s, most "band" instruments were built to A440. (My tenor sax was made in 1934, and was(/is?) "in tune" at that frequency.) Anyone who played with a combo that included an "untunable" instrument, like accordion, cornet, clarinet, marimba, etc., would pretty much need to tune to them, so you can probably assume that your dad's "radio pitch" was pretty close to that tuning.

The remaining question seems to be "what was your "regular pitch" that was a semitone lower?"

John