Well, that's very specific case to be honest. In that case you can just download whatever you want beforehand, from soulseek, for instance. Generally people make preparations in advance for such things.

Zotify works very well at downloading Spotify lists, from playlists to whole discographies. You have to sort the output a little as you'll often get multiple copies of tracks due to remastered editions, songs released as singles etc. But overall it's an incredibly easy way to download music.