I'm not sure this is possible. How can a sound be "content-less"? The sound is the content.
It's possible for a written word (such as "lorem") to be content-less because a written word is simply a string of characters, and strings of characters by themselves don't have meaning unless they are placed within the context of a language. The content of a written word isn't the string of characters of which it's comprised, it's the meaning imparted to that string of characters by the language. For example, the string of characters "hablar" has no meaning until placed in the context of the Spanish language---if you don't speak any Spanish, "hablar" has as much content as "lorem".
But in music, the sound itself is the content. How could it be otherwise? I'm trying to imagine myself hearing your synth demonstration. I'm sitting and listening, and the synth begins producing sounds that "sound real" but don't have any actual content? What does that mean? This is where I get hung up: how can I possibly not hear those sounds as music?
Maybe you could give an example or two of the kind of thing you're looking for?
Update: What Is the OP Looking For?
The discussion with @Raskolnikov below has helped me to clarify some thoughts, so here goes:
For those of you who may not be familiar with lorem ipsum text, the idea is this: imagine (for example) you're a web designer tasked with designing a client's website, and you've reached the stage where you want the client to evaluate some designs you've put together. So you use lorem ipsum text wherever text would appear in the design. Why? Because it looks like normal English text, but isn't actually real text. This accomplishes two purposes:
- Lorem ipsum gives the client a realistic idea of what the final website will look like when the real text is in it. Randomly generated strings of characters don't look realistic: the words are too long, there are too many consecutive consonants, and it just looks fake. Lorem ipsum, by contrast, is very carefully constructed to look like real English text. You could, of course, use actual English text---say, a passage from Moby Dick, which looks like real text because it is real text.
- But lorem ipsum is better than a passage from Moby Dick because it avoids engaging the client in reading the actual text (because you can't actually read it). This is important, because you don't want the client, while evaluating your website design, to read the text and become distracted by thoughts of white whales. When you're presenting the design, the content isn't the point---the design is, and actual text distracts the client from evaluating the design.
Ok. So the OP has a synthesizer they'd like to demonstrate (to a customer, a supervisor, or whoever), and they need some sequence of sounds for the demonstration. This sequence of sounds must do both these things:
- Sound realistic. The listener should hear the demonstration and think, "yeah, I can use this to make music" and not "what am I ever going to use this for?"
- Avoid engaging the listener with the music. The OP wants the listener to be thinking "wow, what cool things this synth can do" and not be distracted by thinking "wow, what great music!"
I don't think this is possible. I think any sequence of sounds that sounds realistic enough to convince the listener they could make effective use of the synth will (or at least might) also engage the listener in the music those sounds are making. Personally, I know I, at least, would definitely be distracted by the music.
So What's the OP To Do?
I think the best thing is to go ahead and engage the listener in the music. Choose music that's obscure and unfamiliar, but still worth listening to---maybe even compose some original music. After all, the ultimate goal is for the listener to come away from the demo thinking "I could use that to make my own music." By choosing something unfamiliar, you're less likely to lose the listener in humming along, but you'll still leave him/her with the idea that your synth can be used to make real music, and that's exactly what you want them to think.
