Vintage Simmons Drums (UK) Users Group

Hello to all in SimmonsVille!  I have a Simmons SDE which I trigger 
with various percussion controllers.  I bought it brand new a few 
years back...it had been purchased new by a local music store back 
in the '80's, and for years sat around, unable to sell.  And then we 
found each other.  Anyway, the manual is well written and helpful, 
but I cannot understand the "AUDIO INPUT" 1/4" female jack on the 
rear panel.  What was Simmons' intended use for this?  Ihave been 
unable to figure this out (and nothing much on it in the manual!)  

Any help whatsoever would be appreciated.  Thanks.

Christopher Cathode.