Most analog gear has SOME type of temperature control. Tempco resistors (low resistance change with temperature), thermisters (couple a positive response to a negative response to cancel out) or other techniques (e.g. heaters - get the circuit up to max temp asap and keep it there).

But none of that prevents temperature differences, they just control for them. And you wouldn’t use temp control everywhere - just where it’d effect the sound dramatically i.e. keeping your main voice oscillators in tune, not keeping your cowbell at a precise frequency