Thanks for both of you !
I would not have succeeded to find out the reason for this problem by myself in a reasonable time.
not so obvious features during their lifetime. As csound is in principle an old system there maybe some of those
surprises hiding there waiting to be revealed.
One problem in csound is also the difference between the execution environment and the programming language itself
compared to some other languages, e.g. java.
I hope the manuals and examples clarify my understanding.
( But of course as usual, to read manuals, is the last option 
)
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