Music starts early


I have noticed this for some time but never got around to asking the question. Some LP's that I play, I will hear faintly the music start. Then all of a sudden the music does start. Does that make sense? In other words. At the start of an LP. You will hear very quietly the song start. Then the real song starts at the correct level. What is up with that?
scottht

Showing 1 response by scouser

Having spent 35 years as a Producer/Recording Engineer, I think that can shed a little light on this phenomena?

It is, indeed, known as 'pre-echo' and one of the main causes has to do with how the original master tape was wound onto its reel and stored. It is common practise in the recording industry to 'tail wind' tapes to ensure that the results of this pre-echo phenomena are not as much of a problem. I'll explain:

What is actually happening is that the magnetic information (music) is being transferred between the thin layers of magnetic metal oxide of the recording tape. Professional recording tape is commonly a mylar or plastic composite 1.5 mil thick, with some of it - for longer recording times et cetera - being only 1 mil. I used the latter extensively for live recording and the former for studio recordings. This transference of magnetic information is a natural occurance, given the nature and physics of recording tape. If the tape is rewound, after use, back to the beginning of the music (head wound) and stored this way, any transferred information will be printed through (known as print through) onto the tape, appearing before the original information from which it was copied. This is what you hear as pre-echo.

In order to minimize the effects of this, tapes are usually wound 'tails out' or 'tail wound' and stored this way. In order to replay the tape it, of course, must be rewound to the beginning. Information that magnetically transfers through the layers (print through) is, for the most part lost in the decay of the music that proceeds it. The volume and frequency of the information, as might be expected, is also an important factor, with loud passages of music being the most obvious ones to transfer between layers.

Another trick to circumvent the phenomena was to edit the leader tape (which is just a plastic or paper tape of the same width as the recording tape being used) right up to the downbeat of the track. This works, but it is always a good idea to leave just a little bit of tape - 1/8" to 1/4" is enough as the tape is travelling at 15ips or 30ips (Inches Per Second) - ahead of the first note, just in case the tape curls or otherwise becomes damaged at the point of the splice. The problem was that sometimes this master tape was copied as part of the disc mastering process in order to document the various changes that might have been made - equalization, limiting/compression, volume and fades and/or re-sequencing et cetera. This new version of the master tape would then become the official Mastering Tape for that project and, at that point, you once again have the possibility of pre-echo.