I have had pietschmanni for several years and they do vocalize often and for a number of reasons. I have witnessed the breeding of my pietschmanni several times and every time they vocalized but it was a barely audible almost grunt nothing like the loud sound you mentioned. During breeding they usually signal to each other through tail wavings and not so much sound. I have noticed that when my female is not receptive she will scream when the male is chasing her. They also vocalize for dominance/territorial reasons and that is usually louder and sounds a lot like what your male was doing. I only noticed this when I first got my pietschmanni and they weren't quite used to seeing each other yet. Mine usually chirp every night after I spray them also. It sounds like your male may be interested but believe me nothing is going to happen until your female is ready. All the successful copulations I have witnessed resulted in the female signaling first.
-Matt
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