Since this project uses Flash those on Linux may want an alternative
https://tiliado.eu/nuvolaplayer/
Edit:also tomahawk. It has come a long way since I last used it and it is probably better than my original selection at this point.
IMO it is way better because it supports 90% of streaming clients (and its not hard to add them if they aren't)
This app is horribly defective you should report it to its creators in hopes of it getting fixed.
In the meanwhile how about sending it to the scratchpad? Does that work?
This also looks interesting https://tiliado.eu/nuvolaplayer/
Not getting involved here, but you mentioned running Evernote in Wine, so I thought I'd pitch in on that - use NixNote if you're into Evernote. Perfect sync with your Evernote account, perfect syncronisation (as far as I can tell across the web, Android and occasional iOS use) and even a few features that don't appear on the official client, such as selective syncing of shared books and database encryption.
It's pretty excellent. Yeah, it needs Java, but there's slow progress on NixNote2 which is going to be GTK native.
[Edit: Oh! I see you mention media keys on Spotify too - don't bother with the native client, and instead run Nuvola. Pretty superb wrapper and you'll get media keys/volume manager integration regardless of whether you're a Spotify, Rdio or Google Play Music fan. Or many others.
Honestly, I tend to find that if anyone has an app that they "simply can't live without", you're better off getting them to pay the Windows tax and live in anti-virus, constant reboot hell, rather than convince them to try Ubuntu, or whatever your distro-de-jour happens to be. It's a big of a cop out, but at least you don't end up tarnishing its reputation, so I'm pretty much with you on the general tone of your comment.]