Here is a fascinating revelation about how radio station tapes were made...  This particular company is only one of several. Of the many different companies I have collected tapes from, these are generally not the best sounding.  And after hearing them for years even on the radio back in the 70's, I now know why they needed a loudness button to sound right...

http://www.drakechenault.org/textpg.html

Great read.