I was surprised to learn that 50Hz was common in Southern California.
Southern California Edison used 50Hz until 1948 - and I have evidence
that the transition to 60Hz was not complete until late 1949 (at least
in the area that served Beverly Hills and some of the film studios).

~ Eric Jacobs


On 11/27/15, 10:05 AM, "Association for Recorded Sound Discussion List on
behalf of John Haley" <[log in to unmask] on behalf of
[log in to unmask]> wrote:

>The fundamental of the hum, at either 60 cycles or 50 cycles, is still one
>of the most reliable "clues" to getting the pitch "right."  All of the
>issues discussed mean that this issue will always be something of a
>struggle, and certainty is not always guaranteed.
>
>Pitch has been standardized, tho not always reliably, at A = 440, since
>the
>1920's, but of course there are exceptions.  Several major orchestras
>(Boston and Minneapolis, for example), deliberately tuned sharp in the
>1940's to get a more brilliant sound.  But unless a reason for an
>exception
>is known, A=440 is still the best choice in many instances.  For example,
>studio-made pop records that include studio musicians, made during the
>1950's will not likely be tuned oddly.  But "in the field" folk recordings
>or gospel recordings could be anything (unless there is an electronic
>organ
>being used, which might be reliable).  Church pianos are notoriously not
>tuned for years, and over time a piano will often sink in pitch, so if the
>piano is out of tune generally, look out.  But it is always good to check
>the hum.   It really should not vary much from 50 or 60.
>
>On vocal recordings, listen a lot to the accompaniment!
>
>Despite all these problems, getting the pitch "right" is one of the most
>critical things an audio restorer has to address.  Changes of even a
>fraction of a half step can make quite a difference, particularly for
>human
>voices.  In today's world, it is a real sin not to at least try to get the
>pitch right, and I mean really right, not within a "range" of right.
>
>I am restoring a mono RCA LP right now from the early 1950's, a
>compilation
>of the same artists, obviously recorded at different times and places as
>the tracks do not share the same "sound" for the space they were recorded
>in.   The first two tracks on Side 1 required a drop of 4%--they were
>playing way sharp, even tho I dubbed the record at 33.33 RPM.  I thought,
>OK,since the first two match, the rest should be the same.  Nope.  The
>next
>track required a correction of -1% to be dead on pitch, etc.
>
>Best,
>John Haley
>
>
>
>
>
>
>On Fri, Nov 27, 2015 at 12:42 PM, Jolyon S Hudson <[log in to unmask]>
>wrote:
>
>> Dear Andrew
>>
>> Sorry for going off at a tangent, easy done!
>>
>> It is possible that the power supply was not all that it could be. It
>>may
>> have
>> been expedient to either drop the frequency or, more probable, the draw
>>on
>> the
>> power stations was such that the generators lost momentum at certain
>>times
>> in the day.
>>
>> This is what happens even today when a blackout is tripped - too much
>> energy
>> being pulled from the grid and the network collapses as generators can't
>> keep
>> up with the demand. To alleviate this you can drop the frequency.
>>
>> I don't know enough about the power supply in Argentina I'm afraid but
>> knowing that between the early 1930s and 1990s the Argentine economy
>> progressively deteriorated I don't doubt that the power supply was not
>>all
>> that it
>> should be.
>>
>> The power supply in the US and most other counties would be fine most of
>> the
>> time. However during wars, economic problems, lunch time and dinner time
>> (nice combination of events) things can droop a bit.
>>
>> I don't think that the frequency of hum is a sure way of getting the
>>pitch
>> right in
>> recordings but it is fairly accurate most of the time but not a silver
>> bullet.
>>
>> This or a combination with other factors could be part of the answer.
>>This
>> is
>> why a number of recording companies kept to weight driven recording
>> equipment as it theoretically guaranteed a constant speed.
>>
>> Jols
>>
>