Well... theres not really a place you can get them. You make them. Heres an example... You can download souund that is an .mp3(music file) or .wav(sound file) file and use it by importing it ( f12 in world editor ) and then going to the Sound Editor and right-clicking on the sound and then click use as sound. You can change the speed of the sound by double clicking on it and changing the pitch. The change ranges from 0.0-2.0, 1.0 being normal. To play this sound as a LOOP music action, go to events, then periodic event, then place the time of the music as the loop time. As the action, go to Sound-Play Sound. Click on the Soundbutton and then go to variables and set it to the music that you've imported.
If you would like to have it as an effect sound... heres an idea, as an ability sound, then do this.
First, import a sound of .wav(sound file) and import it ( f12 in world editor ) and then going to the Sound Editor and right-clicking on the sound and then click use as sound. You can change the speed of the sound by double clicking on it and changing the pitch. The change ranges from 0.0-2.0, 1.0 being normal.
Make a trigger like this.
Events
Unit - A unit Begins casting an ability
Conditions
(Ability being cast) Equal to ABILITY HERE
Actions
Sound - Play SOUND HERE<gen>
Special Effect - Create a special effect attached to the weapon of (Casting unit) using EFFECT MODEL HERE