To be most useful, it should be a short snippet that you throw away after listening. So no pressure!
I went to a lot of trouble years ago to come up with a way to easily record a snippet of piano. Basically a Boss loop pedal and a mic under the piano and a little amp and speaker. So all I have to do is tap the pedal to start recording and again to stop it and playback. Couldn't be easier. This is a throwaway audio recording, since I have no way to save it - and wouldn't want to, since that is not the purpose. It is just to record a snippet, immediately play it back, and critique.
It is still sitting there under the piano. I go through periods of using it, then lose interest, since the recording tells me what I already know by listening critically as I play. But I do have years of experience listening. It was more useful years ago. I still keep it around and use it now and then.
Of course if you are a digital guy there is probably an easy way by just pushing a button. Or come up with an easy way to do it with a phone.
