Found an article in Wikipedia about Paulownia. It says that Paulownia is the fastest growing hardwood and compares it to balsa. It is almost twice as dense as balsa and has a higher strength-to-weight ratio than balsa.
The following is copied from the Wikipedia article.
Japan: An Illustrated Encyclopedia states:
A Japanese Kobundō (小分銅), 95–97% gold, "Paulownia" Kiri (桐) mark, Kikubana (菊花) emblem, 373.11 grams, Japan
It is important in China, Korea, and Japan for making the soundboards of stringed musical instruments such as the guqin, guzheng, pipa, koto, and gayageum.[5] More recently it is used as body material for low-cost electric guitars,[21] as the core for lightweight touring skis,[22][23] and for surfboard cores.[24] It is used in guitars as the core body, then laminated under a more durable wood.[21]