Iain Churches wrote:

"Phil Allison"



A LOT of LPs were sold as "mono-stereo compatible" - meaning the vertical
modulation
had been supressed, at least at low frequencies, so the mono PUs would not
miss track or badly damage the grove.

I don't know how records were cut in Oz, but in the
UK the LF was not supressed, but summed as L+R (lateral).


** Read what I wrote slowly.

It says vertical modulation was supressed at low frequencies.

So out of phase or single channel bass was not cut into the groove - summing L and R at low frequencies before cutting did the trick.


Anecdote:

I once had a customer who owned a small recoding studio ( he was able to cut disks on an old Ampex lathe too) and he had made a short musical tape in stereo to be played on FM radio as a commercial.

He rang me in a panic one day saying the FM station had rejected his tape, claiming is was "out of phase". So I went to the studio, checked his set up and listened to the tape on headphones. When switched to mono it sounded fine, so was not out of phase.

I then rang the FM station and eventually go onto the guy who had condemned the tape. He explained that his stereo modulation monitor showed the tape was OOP.

When pressed for more detail he grudgingly went on to say that the L channel meter regularly a read higher than the sum meter and this meant it was OOP.

The problem was simple: my customer has panned the bass guitar hard left in the mix, the piano hard right and drums in the centre.

He re-mixed the tape with bass in the CENTRE and it got played on air.



..... Phil