"音"牆！

https://www.facebook.com/JBLsynthesis/photos/a.295368293812720.93810.223307231018827/1084164848266390/?type=1

"41 years ago today, the Grateful Dead debuted the Wall of Sound, a monstrous live sound system designed by Owsley Stanley. "

該是指1974/4/9，
這，樂手在喇叭前，啊？