Using applescript to control an application which does not support it
The only way I am aware of is using UI Scripting (old link but still useful) via the dictionary of an application called "System Events". In substance, this allow you to make a script that click on a given button or press a given key. Unfortunately, you'll need to activate Simfy to send the keystroke (but you can automate it and automate a switch to the preceding frontmost application as well).

Remote Buddy allow you to send a keystroke to an application without activating it. You can then trigger the Remote Buddy action via AppleScript. But that seems overkill here except if you use Remote Buddy for other things already.