Roland HP-507 Expression Pedal

[michaelmouse73]

Hi, does anyone know if I can use an expression (volume) pedal with the HP-507 digital piano. There's no expression pedal input. It's for when I go onto play the organ patches which are not touch sensitive. I know I can attach an analogue pedal to the outputs, but that won't affect the internal speakers. Would a USB pedal work? Thanks.