Add to cart Autoharp Backer Board Osc... $25.00 A backer board serves to increase the loudness of your autoharp due to preventing absorption of energy from the vibrating back. It also seems to add to the bass response, probably due to a proximity effect. The increase in loudness and the fuller bass voice are very noticeable. Shipping costs may vary and you will receive a refund or request for additional funds through PayPal. Backer boards behind autoharps are not a new invention. They have been used by various players for years. Ours have some advantages that make it desirable. 1. Light Weight (17 ounces) 2. Open to air circulation. A solid board cuts off air circulation. Ours has enough holes to prevent that so they don’t feel hot when you hold your harp to your chest. 3. They do not interfere with the fit of your autoharp in its case. 4. They attach without any modification or damage to the autoharp and remove easily. They are avialable in either the Evoharp version or the OS version.