Amdrum was probably Cheetahs version of the SpecDrum (As revealed on the PCB "AMSTRAD SPECDRUM")
No other software than Aside of Cheetahs own sequencer is know you can use comme commands of the RSX ROM for LambdaSpeak III to use the Amdrum.
Now, thanks to Jose Leandro, the hardware specialist of the spectrum, with his famous page :