How Do I Increase The Font Size In Spotify?
There isn't a perfect solution, but it is doable. Find the Spotify app in your Applications folder. Hold Control and click once on the app then select Show Package Contents. Then navigate to Contents > Resources and find the file named skin.xml. Open it in TextEdit. This file will let you change the look of almost anything in the Spotify app.
To change the sidebar font size, look for the following:
<font ci="SidebarRowFont" size="11" color="#dddddd" shadow="#333333" />
I changed the size to 14 but you can try any size. Just save the file and then restart Spotify to see the changes.
To change the main font size for song listings, look for the following:
<font ci="MainlistRow" color="#dddddd" size="11" shadow="#333333" style="shadow_up" id="mainlistRow" />
Again, increase the size, save the document, and restart Spotify.
One note: if you update Spotify these changes will be erased. I recommend keeping a document with notes about whatever you changed in skin.xml so you can easily change it again next time you upgrade the app.