The original sound of the instrument is bypassed and the volume knob allows to blend in the effect sound. The effect is triggered when you kick the footswitch and it hold the note or the chord you were playing when you kick. The sustain can be infinite and you continue playing above this sound. Of course, you can change regularly. It's not a looper and I'm not sure a looper can does it as easily as the Freeze does. Very nice but sometimes a bit hard to master because if you kick in the effect too soon, it can results in weird sounds due to the hitting string little sound. So you need to work it a bit in order to switch it on at the right moment. The original sound of the instrument is bypassed and the effect is digital so it can sound a bit artificial. If you play over, it's hard to notice. The switch allows you 3 modes: - Slow: you have a fade in and a fade out effect. You can set up on of the 3 different speed. It works as long as you keep your foot (or a brick or wathever you put on) the footswitch. To catch another sound, raise your foot then push the footswitch again. - Fast: same as slow but without the fade in/fade out. - Latch: you don't need to keep your foot on the footswitch and when you kick, it takes the new sound so it's good to chain the sustained sounds when playing. you have to double kick to stop it. My advice is to put in at the end of your pedalboard. This way, you can catch an overdriven sound (or delayed or octaved...) then play over with clean sound or do the contrary. You can find mods with blue LED instead of the red one, silent footswitch or external footswitch. Easy to use but sometimes hard to master, it provides a nice effect to feed your imagination with.