Your saying - "Suppose the song is fast and RPM would also be more. Like wise for slow songs or sad songs the RPM would be less." Irrelevant statement with insufficient experience. There is no different RPM for fast music and slow music.
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It was a mechanical manual gramophone in which we had to wind a mechanical spring (like we did in manual watches) and once wound it will go for 2-3 songs. We had small steel needles which were to be fixed on the bottom of the horn like device which produced sound when the needle moved on the song track. The sound of that gramophone was very clear and loud and almost half of our village was able to hear the song and many times people came to see that sound machine.
As there were different types of record were available so we had to select the speed accordingly. There was a lever to change the speed of the round turn table on which record was to be mounted. If I remember correctly, the record for 78 and 45 rpm were very common. If you play the record in wrong speed the sound was highly affected and the voice of a female was changing to almost that of male.
This, I am talking of the year around 1960 and we did not have a water or electric line in our village and this piece of gadget was an amazing thing in that time. It was HMV make and costed about Rs 200.
Today your thread has rekindled my memories.
Knowledge is power.
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Hopefully we never going to evident these again.
I tried to find a record-player for old days' sake during the early 2000s in Delhi. But even after considerable search, I couldn't find one for purchase. Only a very rich person who was a collector himself, had an old record-player, but that was not for sale.
Beware! I question everything and everybody.