I haven't really even looked at the csound code, but from what I understand
it is only the signal varibles (a-type, k-type, i-type) which are set as
single precision floats. There is nothing to stop ugens from using doubles
internally with inputs and output as singles, in fact I asumed that doubles
were used for filter coefficiants. What advantage would there be in double
precision signal varibles. The disadvantages would be slower code both from
the actually precision as well as more (2x) cache misses, and a whole lot of
work.