Assuming you are picking up where you left off at the end of Title Update 2.
Fast Travel to Bar. Talk to Scrubman. He will ask you for a book.
Fast Travel to Kiryat Temple. Go inside and grab the book off the bench.
Fast Travel back to Bar. Talk to Scrubman. Give him the book for a crown.
Fast Travel to Pentatonic Temple. Talk to Pentatonic Guitarist and trade him the crown for a Tuning Fork (camerton).
Fast Travel to Home. Go inside and go right into the Studio. Use the Tuning Fork (camerton) on the Piano.