Disco singles -- I've never heard of any "standards" as far as modulation or bass boominess or the 
like. One of my high school summers when I worked at Sigma Sound NYC, I got to go-fer around some of 
the disco-remix sessions that went on there at night. I saw some very creative use of tape loops and 
other interesting pre-computer ways to stretch phrases, shift beats and the like. All in the 
"service" of utterly awful music! These masterworks would get polished off just in time for 
Frankfort Wayne mastering to open up. Those guys would cut a record as loud as was trackable with a 
DJ turntable and the producer-type would rush off with a few laquers and perhaps a bag of chemical 
goodies to hand out, hoping to get the laquers spun on the dance floors that next night.

George is correct that 78RPM would have been ideal for disco singles but I don't think this would 
have been practical given that DJs would switch between LPs and 12" singles and 45's, all 
microgroove, and not have to change cartridges in the process. The few discos I experienced in those 
times, feedback wasn't an issue because the DJ booth was highly isolated. I recall some 12" singles 
being 45RPM and some being 33RPM (especailly the 15-minute "extended trippy mix" versions, which 
made very liberal use of tape loops and clap machines and the like).

I recently noticed that there is now a "DJ/mixmaster" app for the iPhone, allowing cueing and 
scratching and mashing of iTunes files.

-- Tom Fine

----- Original Message ----- 
From: "George Brock-Nannestad" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, October 14, 2009 8:37 PM
Subject: Re: [ARSCLIST] late date 78

> From: Patent Tactics, George Brock-Nannestad
> Hello, Milan Milovanovic asked:
>> Speaking of micro versus wider grooves, would wider grooved cut record be
>> more resistant to micro scratches and easier to get clean from dust etc.
>> than "microgrooved" LP record?
>> Also, would 78 rpm speed be more suitable for recording/reproducing
>> especially at the last 1/5 of disc with no groove distortion added in this
>> area (often connected to ordinary 33 rpm records)?
> ----- I have in front of me an article printed in Audio magazine in April
> 1963. It is "A 78-rpm Stereo Record" by Allan R. Keskinen. The record itself
> is a test record that permits instantaneous evaluation of a stereo cartridge,
> and he says:
> "    In the preparation of this record, the 78.26-rpm standard record speed
> was chosen in order ot reduce stylus-tracing-geometry and wavelength effects.
> The resulting long wavelengths and the large groove size used, reduce tracing
> distortion to a minimum and extend record life. The bottom of the groove has
> a radius of approximately 0.0002 in. permitting use of styli as small as
> 0.0005 in. without danger of bottoming.   .....".
> This is obviously not a stereo record in the commercial sense of the word,
> but the article shows the thoughts that decided the selection of the highest
> speed. The article as such is otherwise very good and instructive. Keskinen
> was the chief engineer at Astatic.
> The speed, groove spacing and modulation, and duration are all interlinked,
> and the purpose decides the compromise that is used in practice. In my view,
> the best present sound is obtained from a disco single, which has a wider
> groove, a higher speed and also a lower cross-over frequency than an LP
> because it permits higher amplitudes at lower frequencies. This means that
> the DJ does not have to use so much bass amplification for a given bass
> output, and that reduces the risk of acoustic feedback to the pickup via the
> turntable. And I think that this freedom from feedback was what decided the
> issue for digital recordings (=CDs), not anything to do with quality as such.
> I do not think that there is an industry standard covering disco singles, but
> I would like to be corrected and to have somebody give a reference.
> Kind regards,
> George
>> ----- Original Message ----- 
>> From: "George Brock-Nannestad" <[log in to unmask]>
>> To: <[log in to unmask]>
>> Sent: Thursday, October 08, 2009 6:52 PM
>> Subject: Re: [ARSCLIST] late date 78
>> > From: Patent Tactics, George Brock-Nannestad
>> >
>> > Hello,
>> >
>> > Mike Biel wrote:
>> >
>> >> Theoretically the best sound at 78 would be with a microgroove size
>> >> groove since it would be capable of higher frequency response than a
>> >> wide groove, or a microgroove at slower speeds.
>> >
>> >
>> > ----- now, I am speculating why this should be so. I do not understand why
>> > a
>> > microgroove should give a higher frequency response than a NORMAL groove.
>> > It
>> > has to do with the maximum acceleration of the tip and the ability of the
>> > tip
>> > to trace precisely the groove shape. If the smaller radius of an
>> > elliptical
>> > stylus (or the radius of the edge in a line contact stylus) is able to
>> > trace
>> > without error a curve in one flank of the groove, it does not matter
>> where
>> > the other flank of the groove is.
>> >
>> > If microgroove is associated with a higher groove pitch (which would
>> mean
>> > well above 200 grooves per inch), then the maximum amplitude would be
>> > reduced
>> > compared to the ca. 100 grooves per inch in a traditional 78 rpm record.
>> > If
>> > we maintain the 100 grooves per inch but reduce the groove width and
>> > depth,
>> > we would have more land to use, and the modulation could be higher,
>> which
>> > would give a low frequency advantage. That is the rationale behind disco
>> > singles (albeit at 45 rpm). And all of this without variable groove pitch.
>> > If
>> > that is used, then we are even better of, bass-wise.
>> >
>> > Kind regards,
>> >
>> >
>> > George