oh yeah - a passive transformer is not gonna do that “in general.”
it will shift voltage up/down, but with a corresponding increase / decrease of current flowing from the source.
a low-impedance, powered (e.g. line level) source will [likely] have some sufficient current “on tap.”
a high-impedance, passive source like a guitar pickup can only deliver whatever power is actually being generated by magnets/strings. so instead of “stepping up” the transformer just dissipates some power.
(or something like that.)
anyways, for instruments you probably want some form of active preamplifier stage. (norns inputs have no gain at all, so just matching impedances will be insufficient to capture low-powered signals.) it’s a classic DIY project[*] if you’re interested that and sort of a perfect way in to analog electronics. (also, cheap.)
there are of course many commerical options as well, including a recent rash of weird tiny headphone guitar amps with digital FX. (imho there is something a little creepy about the un-serviceability of these things, shrug.)
([*] NB that for this particular circuit you would want to mod it for more gain by replacing R2 with a large-ish cap.)
(here is a reasonable-looking opamp-based circuit. though again you probably want to make some modifications for more gain - in this case increasing R2 or decreasing R1.)
