Analyze an explicitly supplied audio/video attachment without saving a score or spending transcription credits. Returns measured length, account processing limits, tuning offset, level, polyphony and an engine recommendation. instrument is piano, guitar, voice, band or other; unresolved classification yields no engine. Sheet music is not accepted. analyze_instruments defaults false; true adds bounded local candidate analysis of at most 300 seconds and three minutes processing. Candidate scores are uncalibrated.