The velocity of {HEAD ~ the progression} is determined by the given distance of {TAIL ~ the fixtures} at a given frequency 
The velocity of { HEAD ~ the progression } is determined by the given distance of { TAIL ~ the fixtures } at a given frequency
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH