Sorry, I may have misunderstood your question. Reading it again I saw you wrote
Buffer 1 is the existing sample from my computer, and 2 is made from Signal. The gaps you hear in the audio is when Playbuf plays from buffer 2 , so there is no audio.
Does that mean only the buffer that you were trying to fill with a signal isn’t audible in the recording? (I must confess I didn’t test your code)