function is overriding a variable setting

i want to compare an audio stream prior to and after an audio filter function called F2.process

the problem is that, when i bar out the second line, the result array is the original array, and if i write the filtered array to an empty variable it also changes the source array variable.

The F2.process function doesnt write to the input variable, i dont know what's wrong, no matter what i do, i can't use the filter function line without keeping the original input signal:

 var setmono2 = setmono;      // original float[] prior to filter function
 var setmono3 = F2.process(setmono, F1freq, F1type );  //filter
 var resultArray : float[]  =  interleave2(setmono2, setmono2); //outputs setmono3