Limitations of categorizing by tone divider technology

If you are unfamiliar with an organ, knowing what type of tone generator it has can tell you a few things about it. First of all, it can generally tell you the age of the instrument. Wurlitzer adopted new technology fairly quickly, in hopes of reducing manufacturing costs. Then, after a year or two, Wurlitzer would phase out the old technology. So, in general, reed organs were earlier than vacuum tube organs, which were earlier than discrete transistor organs, which were earlier than analog integrated circuit organs, which were earlier than digital organs.

The earlier technology generally took up more space than later technology. Vacuum tubes take up a lot of space, and they run very hot, which limits the density of the surrounding circuit. Transistors occupied a lot less space, and integrated circuits could contain thousands of individual transistors encapsulated in a tiny plastic box. So, in vacuum tube organs, a lot of the interior cabinet was occupied by sprawling circuits that didn’t do anything other the basic organ functions of generating the signal and then amplifying it. Once the footprint of the tone generators and amplifiers was reduced—first by discrete transistor designs, then by ICs—the organ gained a lot of extra space that could be occupied by additional voices and effects. That’s why you’ll find features like Banjo in the IC organs and not the vacuum tube organs. We think of tube instruments as simple and stripped down, but that was for reasons of cost, and not a lack of desire to make synthesized sounds.