> Thomas, I ran it in X trying each 'out' statement. Ouput appearance and
> sound was the same in both cases. I'm using the unofficial Linux
> distribution 3.54.0.0c.

I just downloaded this unofficial distribution and compiled it
with egcs-2.91.66. For me, the 'tanh' still does not work. Same
spike-output as with the canonical version.

Do you see a difference when setting a low krate (i.e. ksmps=200) ?

If not, it is a problem on my linux box. I suppose it has to do
with the math library. Which libc/libm are you using ?
I have libc.so.5.4.46 and libm.so.5.0.9. I don't think it's
the compiler, as the problem occured with gcc-2.7.2.1 and with
egcs the same way.