A while back I ordered several vactrols from an electronics company. Many may not know what these are but those familiar with the synthesizers of Buchla will probably recognize the name. Another name for them is optocoupler. Simply, vactrols are and LED combined with a photocell encased in a shell so that no light gets in from the outside. The practical reason for these is to isolate a higher voltage circuit from a lower one. The musical reason is that vactrols sing. That is, they tend to chirp when used to control filters and have a rather distinctive sound.
I used to be fascinated by waveforms because I fell into what I call the fourier trap and believed that all sound is represented by fourier series. If you don't know what this is don't worry. It's a staple of additive synthesis but it defines static waveforms. Truth is, sound is dynamic. When we hear and instrument, much of what we really identify with is the attack transient, the first part of a note. Some might thing of a vactrol as only a switch, LED on/LED off but it's that period of less than a second that makes all the difference.
Stephen Hawking made physics popular with his "A Brief History of Time". In many ways, Road's "Microsound" does this for sound. We realize, the importance of the attack transient. Analogue synthesizers lend themselves to using this transient by controlling sound with voltages. Voltage is well, electrons which are very very quick to say the least. Simply put, this means that analogue circuits respond quickly and can create all sorts of interesting transients. This is often done with pitch. Think of how musicians as well use variations of pitch in the early transient of a note to add expression.
Digital electronics have trouble with transients at times because they require CPU cycles where analogue circuits don't. Until we have much faster programs, I think this is where analogue circuits have distinctive advantage and when we are speaking of a brief history of sound, analogue is king.