What's wrong with this expression:
transform.scale+thisComp.layer("solid").effect("Sound Keys")("Output 1")
also tried these, but got an syntax error:
s = transform.scale+thisComp.layer("solid").effect("Sound Keys")("Output 1");
[s[0],s[1]]
and
s = transform.scale+thisComp.layer("solid").effect("Sound Keys")("Output 1");
[s,s]
s = thisComp.layer("solid").effect("Sound Keys")("Output 1");
transform.scale + [s,s]
Dan