The controls in cmus are laid out like a traditional VCR/tape-player from left-to-right in the bottom corner of a traditional QWERTY keyboard:

z=prev &#x23EE;&#xFE0F;  
x=play &#x25B6;&#xFE0F;  
c=pause &#x23EF;&#xFE0F;  
v=stop &#x23F9;&#xFE0F;  
b=next &#x23ED;&#xFE0F;  

I can't say it helps me remember *much*, but at least that's the reasoning behind the non-mnemonic keys.