What's important about synthesizers is the fact that for the first time in history it allowed musicians to control the "character" of sound gradually in new dimensions (the parameters that let you distinguish the same note played on piano, flute, guitar, violin, etc.), creating sounds that were impossible previously and even changing the character of the sound in real-time as another dimension of artistic expression. It's like you played a long note on violin and it morphed slowly over time into a flute and then some instrument that doesn't exist. You couldn't do it before and all these new possibilities and constraints changed music.
Also the particular UI of some synthesizers allowed easy exploration of these new dimensions and that's important too. It's one thing to be able to play any waveform you want (you can do that by editing .wav file in hex editor), it's another to have several knobs and sliders and hear the differences in real-time when you tinker with them.
We can simulate all of this in software but not 100% perfectly.
Even for an almost fully digital synth like the DX7 a bit-accurate emulation is difficult (there is a rich discussion of this in one of the other threads here). For analog synthesizers, there is a lot of character and nuance in the individual circuits that are difficult to capture in a digital model, across all possible configurations. In the mix of a full song though, its not often that people can notice the difference.
Aliasing--the introduction of extra unwanted and generally non-harmonic frequencies--is also really hard to avoid in digital systems. For more esoteric instruments like Eurorack modules or Moog modular synthesizers, the physical interface is an integral part of the instrument--software versions of these exist but are obviously very different to interact with using a mouse or touchscreen.
> Why aren’t all new keyboards (or those other things DJs have on stage) simply software, maybe with a custom input device for easier live use?
For live use this is very common nowadays, though physical single purpose keyboards (even fully digital ones) still are used widely. In a fast moving stage show you may not want to mess around with the complexity of a full personal computer setup. In modern operating systems, even with 100s of processes competing for CPU time, real-time audio may rarely drop out (the result of which is audible clicks and pops), but even this is too risky for a big professional live show.
44000 / 1sec / 1000ms
hopefully we have better latency than that!
But that's not what he meant, he meant that non-real time (soft real time, not even hard real time) OSs pause pretty frequently for relatively long periods. You might not miss any samples at all due to hardware buffering, but the effect on UI is tremendous.
After fiddling around a bit I decided to try the MuQSS CPU scheduler and was blown away. Not only was the scheduled backup unnoticeable, on top of that I could throw a 16 thread compilation job on my 8core/16thread CPU and I'd not notice the system being under load. I might've lost a few frames per secone when occasionally playing some FPS games, but possibly lowered throughput be damned, this was bliss.
Unfortunately it seems to not be updated anymore. So I tried the newcomers on the block, BMQ and PDS. With BMQ I would start dropping iSCSI connections since my PC wouldn't manage to reply to a ping in five seconds. PDS fit better. While MuQSS could handle a load of 40-45 before I started noticing UI-latency, PDS tops off at around 20. And when it starts to stutter, it's worse than with MuQSS, but since it's not that often that I'm at those loads I'm quite OK with the current situation.
All this with untuned schedulers, they might behave very differently with some tuning.
there are some sounds that rely on certain electronic oddities from weird components that cannot easily be modeled in software. some Russian transistors that are used for the polivoks filters are some that I can think of off the top of my head.
personally, I've built a ton of software simulations of hardware equipment, but I still have a tx81z sitting around, and a rack full of eurorack gear. there are just some things I can't get quite right, and some weird things that I doubt I could ever reproduce[1].
we can't accurately model a SID chip in software or fpga due to its weird quirkiness under electrical load, some of the less sane chips are even harder. that's why there's such a demand for weird things that use older chips[2].
1. https://www.nonlinearcircuits.com/modules/p/brain-custard
The main problem with this is that software runs on computers, and sufficiently portable computers are generally just not reliable enough for a lot of live performances.
Keyboard = input device, usually generates MIDI. Synthesizer = creates sounds from scratch, usually generates audio from MIDI.
Some keyboards are not synthesizers (sometimes called a "master keyboard") and you have to plug them into something in order to get sound. Some synthesizers are not keyboards, and you have to plug something into them to control them. For example, the DX7 is both a synthesizer and a keyboard. The TX-802 is a synthesizer but not a keyboard... it is kind of like two DX7s in a 2U rack-mount unit without a keyboard. The Akai MPK249 is a keyboard but not a synthesizer. You can buy a TX-802 and an Akai MPK249 and plug them into each other, and it's kind of like having a DX7.
> Also, in today’s world, do these need to exist in the same form? That is, can’t all these sounds simply be digitally produced rather than relying on circuitry?
Circuit emulation has varying degrees of accuracy. I like to think of digital synthesizers as computers that don't ever need software updates, and are therefore more reliable than software running on a computer. They also often have purpose-built UIs (knobs, buttons, sliders) which are critical to some people using them.
If you are going to make a custom input device, why not just make the custom input device and the synthesizer one single package? This is called a "sound module" -- something that makes sounds but does not have a keyboard attached. They come in both rack-mount and desktop versions.
But the concept is applied in hundreds of fields as you move from curve, to planes to volumes.
The key magic is the sine wave which unlike other curves on differentiation any number of times always produces a sine way due it's deep connection to anything in nature that Repeats.
At least, that is what I recall from my EE classes 35 years ago.
A lot of modern synthesizers or sound modules are basically just software running on CPUs, DSPs, or even FPGAs.
But previously it was all analogue electronics. Which are extremely difficult to perfectly replicate in software and even models of the same synth would sound slightly different due to manufacturing differences/defects.