So, where had I got to with trying to play .SFZ instrument samples on Garageband? After more reading and mucking about than I really wanted to do… success!
Turns out that the isfizz app, which interprets that file format, has a pretty strict folder hierarchy which isn't mentioned in the few scraps of text that pass for its instruction manual. Luckily, I found a passing comment to that effect on a forum, moved the FLAC files to where the app was expecting to find them, and voilà! Or even viola, if I download the orchestral strings files.
It's a bit of a faff to use because it has a set range of notes it will play, so I have to shift the octave for whichever type of recorder I select (unlike every other virtual instrument I have tried so far), but it *does* sound like a baroque recorder!
#SmallVictories