This How To is simple but incredibly valuable to me when I want to record from VSIDO/Linux. I constantly record from Pithos/Pandora and put it on my Nexus for later play whilst practicing my love of golf. (Practice is fun but epically BORING)
Step One:
sudo apt-get install sox libsox-fmt-all
Step Two: Start Any music playing app or online stream such as Pithos/Pandora
Step Three: in terminal run
rec -C 320 callthiswhatyouwant.mp3
My example is
rec -C 320 "Pithos - Classic Rock Station II.mp3"
- this way I can already have it named for my music file structure
Step Four: Enter Pulse Audio Volume Control from any way you want ... from terminal it is
pavucontrol
From the Record Tab and Dropdown area select what is your recording device:

This is what I have on mine, once you have something recording you can see what is there and available
Step Five: Record from terminal for as long as you want ... I have recorded as much as 12 hours at a time with no issues... at 320 bitrate quality that is quite the file size (over a gig, but well worth it)
Step Six: Open any Tag program you like (EasyTag or Puddletag) and tag your file. Then add it to your device or music library and ...
Profit!
This sox manpage gives you all the great details on the different parameters you can use for recording including using flac, ogg, different bit rates etc etc