For completeness, I should also mention another form of flutter called 'scrape flutter' which is peculiar to tape machines and not normally included in traditional wow and flutter measurements. Common causes include vinyl records with the mounting hole stamped slightly off-centre, and tape machines with slightly eccentric capstans or pinch rollers, or varying tape tension. These variations in the recording or replay speed create equivalent variations of pitch, producing a wobbly or unstable sound.Īnalogue tape and cassette machines, and vinyl record players, all exhibit some level of wow and flutter: they are intrinsic artifacts of the technology involved. For the unfamiliar, 'wow' is a slow, usually cyclic, speed variation, while 'flutter' is a faster variation (below and above about 4Hz, respectively). This screen shows a section of of my test Chopin piano recording, with the intensity increased and the correction data heavily smoothed.Īnyone under the age of 30 might be excused for wondering what 'wow and flutter' are, let alone what they sound like! With the advent of the CD in 1983, wow and flutter were effectively banished, but previously they were very familiar parts of all recorded sound, caused by short-term variations in playback speed due to inherent mechanical inaccuracies. Celemony's clever restoration tool invisibly fixes the speed variations that can plague material recorded on tape or vinyl.
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