Having been in that seen for the last few years, here's the deal... You cut 5 songs in 3 hours (demo sessions) you have to be fast and come up with great parts But it HAS to be vibey and cool...you can do fixes, so you don't have to play perfectly every time but it has to be cool and appropriate for the song
Also, you have to have great sounding flexible gear...for example, if this song needs a 12 string electric part, you better have one in your coffin...