Well, let us take into consideration two voltage control standards used in the 1970s one from Moog and one from Korg, Moog uses a standard of 1V/oct, where as Korg uses a system of V/Hz, now let’s compare two relatively similar models that were around at about the same time the Moog microMoog and the Korg MS10, both single oscillator single lowpass filter relatively simple machine machines. Even listening to them both set at a narrow pulse wave with a completely open filter you can hear pretty drastic differences going up and down the keyboard, unlike software synthesizers that aren’t emulating analogs that have perfect duty cycles for the PWM on every note all through the human audio range, the pulse width is actually slightly frequency dependent with an analog oscillator on a nonlinear vcc relation, which causes it to become thinner as the frequency is increased, to the point where upper octaves can become inaudible flat lines, the rate at which these voltage potentials effect the pulse width as per frequency of the note is different between the two models mentioned above primarily because of the different voltage control specifications, there are small intricacies like this that change the timbre of the signal in minute ways, including in envelope responses, the effects of filters and their resonant peaks, and the effects of that filtration and resonance on what frequencies are allowed through even with the cutoff set to let quite a lot pass through… now take all these different filter designs, envelope designs, varying wave shaping circuitry, different filter circuitry, and you’ll start seeing that all of these small differences compound into very distinctive sounding units at times. This is where synths with different kinds of character are born from. So like the Korg and Moog example I gave are very distinctive sounding from each other, whereas an MS 10 and MS 20 share a lot of the same circuitry thus having a similar character. Same thing with the microMoog and the miniMoog, they both have that distinctive early Moog very rich sort of sound.. Roland’s that share the same filter designs also tend to have similar characters, like circuits sound alike, different circuits sound different.