I hope this is the right place to post this, but maybe the Software Forum would have been more appropriate. I just couldn't find any similar questions there.
 
I'm looking for the kind of very very deep bass, almost sub-sonic, practically subterranean, descending glissando (slide) "moan" or "groan" that was very popular in rap and house music maybe 2 - 5 years ago. 
 
I'd like to use that sound just twice in one of my songs. It should ideally start and end on defined pitches and be able to be controlled for length.
 
Would anyone know of something free (or cheap) that's simple to use and would do the trick?
 
Thanks :)
LJ

Check out "Eve of Distortion" on this free loop site.

can you post an example.  i think i know what you are talking about, but wanted to be 100% sure.  If it is what i think, it can be made with many synths  or a sampler. 

if it is what i think, it is typically made using a long tuned 808 sample with long release and portamento/glide stretched over an octave.
 

Thank you very much, Larry Jones and dubdisciple! I'll give both a try this afternoon. :)
LJ

I would use a pitch envelope in Rapture or Dimension Pro. Rapture has a much larger range if you want the note to drop by several octaves.

Good idea, Kev999. Thanks very much!