this one in particular i remember alot from 95 or 96. i always thought it was a reversed bass line, that it could have been in some cases, but i actually know how to make it with the emu's test tones...
what you need is a sample of:
the test tones; sine and square.
place both tones so that they sound at the same time. set them at the origins a3 or a4 whatever you like, just depends how low you want to go.
i added the sine so you can get more boom, but i guess you could do this with a lp square with a clean square on top and octave or two above, just depends on what you want.
now all you have to do is take the squares attack and adjust it until it fades in. you will have to use your ears on this. you don't want to make the attack too lengthy or you wont beable to hear the square most of the time. what you are going for is at least hear it at it's max when you play a quarter note. at least. but really it is up to you. you should also make sure you set the attack on the sine to 5 or so to get read of any pops... it seems it doesn't matter what you do, you just can't get read of the pops on the sines start. just doesn't seem possible.
once you set the attack correctly (of course i am talking about the adsr for the amp) you should get a sound that sounds like the square wave is going backwards. you might also try playing around with the filter adsr and make that do some more stuff later in the sounds "life" for a more interesting "patch"
what is kind of neat about making these "patches" on your emu is that you can control every aspect of the wave. if you have a patch that is using four different waves you can make them all use different filters at the same time. so if you move the mod wheel or whatever you are using for the controller, you can have the first wave go low, the second go high, the third go band, the fourth go shelf/peak. conpletely changing the sound from the orginal...
i will post more "patches" that i figure out later, i thought a simple one might get some people thinking...