A lot of the bands I watch live performances of online have a dude playing synth and he is always tweaking knobs on what looks to be like a guitar stompbox pedal. what is the stomp box that you see on top of a lot of keyboardists' synths. Is it a compressor? I can recognize delay pedals on some rigs along side this mysterious one, but there is sometimes just one on top that doesnt appear (to me at least) to be making any noticeable effect, like phaser or echo. just a query.