Paul at Houston and Paul at JPRC, Houston, Thanks for the loan of the board pair. They worked first time with both guitar and stereo passthro'.
So the software worked ok and the fault was due finger trouble in my setup - not installing all libraries with teensyduino and possibly incorrect expansion of the Zip download file . I have already bought a replacement pair from Pimorini and will solder them when the female headers with the long pins arrive from the same company. Will return the pair v soon. What a relief ! The sound quality is impressive and I'm looking forward to slaving the boards from my guitar effects and FFT sketches. Will post the finished programs.