Possible Clues:

• Device most valued when not giving true output?
• Device that won't reveal anything for a soothsayer
• It may check someone's veracity
• It puts veracity to the test
• Truth machine
• German songs including moving octet which hopes to reveal invention
• Editor elect (anag.)
• Perhaps interviewer's equipment: it works with electrode
• Forensic equipment that is spread about, held up by reader
• One should identify the false wind octet among art-songs