I now have a keyboard without "media" keys, so I came up with a set of global hotkeys that I've set up in my music player and consider quite handy. ("Global" means they work in the entire system, also when player application is not in focus.) I can't remember where do they come from, but I think it's possible that I've seen them somewhere. These are:
Ctrl+Alt+Insert - Play
Ctrl+Alt+Home - Pause
Ctrl+Alt+End - Stop
Ctrl+Alt+Page Up - Previous track
Ctrl+Alt+Page Down - Next track
Ctrl+Alt+Arrow Up - Volume up
Ctrl+Alt+Arrow Down - Volume down
Ctrl+Alt+Arrow Left - Seek back few seconds
Ctrl+Alt+Arrow Right - Seek forward few seconds
My favorite music player is foobar2000. To setup new global hotkeys there:
Select: File > Preferences
Go to: Keyboard Shortcuts
For each new hotkey:
Search for appropriate action using "Filter list by" and select it. Actions for my hotkeys are:
Playback / Play
Playback / Pause
Playback / Stop
Playback / Previous
Playback / Next
Playback / Volume / Up
Playback / Volume / Down
Playback / Seek / Back by 5 seconds
Playback / Seek / Ahead by 5 seconds
Click inside "Key" box and press your hotkey.
Check "Global hotkey".
Close the dialog window using "OK" button.
I'm sure you can do this in other music players as well, like AIMP.