Fred and the Fantastic Tub-Tub

Fred, a young girl, and her Grandpa travel to the island of Papa-Nupi to see, or rather hear, the mysterious Tub-Tub - a plant that flowers every 200 years and which 'produces music so beautiful even the birds in the trees stop singing to hear it.' But even if they can get there, can they manage to bring a recording back with them to prove what they've heard?