That's really big amount of ram. Have you tried to reinstall spotify?
1, Uninstall Spotify from "Programs and Features" in Control Panel 2. Remove all spotify folders on your PC 3. Download and run CCleaner, clean and repair your registry.( http://download.cnet.com/CCleaner/ ) 4. Restart your pc. 3. Install the latest version of spotify.
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Is it turns out every button you press just eats more memory. It is like the program does not have a function to release unused memory. Although I agree with the rest that the history tab takes up a substantial amount more when used.
All in all this isn't an issue for me because I have 12GB of RAM. I have left Spotify on for days at a time and it still seems to run fine.
I attatched some pictures from using the "history tab" method. I managed to double the RAM consumption from .5GB to 1GB in under 2 minutes.