[farshizzo]

You can change the value of MAX_SAMPLES anytime you want. If you want to set it in your callback then you can do the following:

def onKeyDown(key):
	global samples, MAX_SAMPLES
	if key == ' ':
		#Clear samples and start timer
		samples = 0
		MAX_SAMPLES = 45 * 30
		viz.starttimer(1,SAMPLE_RATE)

viz.callback(viz.KEYDOWN_EVENT,onKeyDown)