[sdiy] Importance of Matched Transistor Pair

[Alex]

I'm kind of new at some of this, can anyone tell me what the importance of
using a matched transistor pair in a synth circuit vs. two individual
transistors?

I know that the Roland TB-303 uses a matched transistor and there's a synth
DIY site out of Scandinavia, that sites using a matched transistor pair for
his mono phonic synth. I want to build a modular synth and then I saw this,
can anyone provide me with some background on this on why it's used for
synth design? There are only 3 or 4 matched transistors that NTE provides.

Thanks.

Alex