the cassette tape has been sitting in a box at room temperature for 8 years or so. funny little spores were growing from and had devoured the little piece of felt that cushions the tape against the record/play head so I took the cassette apart and transferred the tape to another cassette with intact felt. no better.
the other thing I might do is get a proper rca-to-mono-miniplug adapter since I only had a stereo-rca-to-stereo-miniplug adapter and I am not sure that only using the left channel gets the same results as a mono plug.
otherwise I guess I'll have to accept that some of the little magnetic bits did not survive storage and if I ever want to hear the drums from Drunken Boat again I'll have to reconstruct them from scratch. this I don't think I could do since I never deliberately wrote the drum patterns to begin with. I started with 8-beat patterns and offset them and cut and pasted them somewhat randomly until I had a couple of 5-beat patterns I liked.
but now it is time to take a break from drum machine fiddling. on to the guitar.