Thanks for that recommendation, really good app. In today’s app landscape it’s almost unbelievable that it’s so polished and free and without ads / signup links / always-on location sharing etc.

It’s not even easy to find. Few months ago I wanted a simple audio spectrogram app, downloaded some which wanted dubious in-app purchases, or had ads. I hadn’t come across it earlier, but Phyfox does what I wanted better and for free.