It will be interesting to see if Jamie can come up with a solution to the slowing-down amateur 
cassette recording. These are common in the world of oral histories. An automated process would be 
great, because I know from experience there is never funding for more than a few dozen dollars per 
tape to do it in quantity. If it's a "bespoke" custom process, the only use will be in rare one-off 
recordings of great commercial value.

By the way, I have noticed there is often ambient hum in amateur recordings, hum found in the room. 
Motor hum from an air conditioner or fridge, hum from flourescent lights. More steady-frequency 
content than you'd think. I don't know what happens to a cassette recorder's bias oscillator as the 
speed slows down. My guess would be that it keeps a steady tone until it konks out, maybe at the 
same time the motor konks out or maybe before.

-- Tom Fine

----- Original Message ----- 
From: "Tom Fine" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, February 27, 2016 6:42 AM
Subject: Re: [ARSCLIST] Cassettes that speed-up---what's up?


> In my experience, the hum level rises as the batteries die. I assume the filter caps get 
> un-energized.
>
> -- Tom Fine
>
> ----- Original Message ----- 
> From: "Nigel Champion" <[log in to unmask]>
> To: <[log in to unmask]>
> Sent: Saturday, February 27, 2016 4:03 AM
> Subject: Re: [ARSCLIST] Cassettes that speed-up---what's up?
>
>
> Hi Jamie
>
> The Nakamichi 680ZX can record and play at half-speed (15/16ips) and has good reviews.
>
> How much hum would you expect on the battery-powered cassette recorder we're talking about here?
>
> Regards
> Nigel
> ________________________________________
> From: Association for Recorded Sound Discussion List [[log in to unmask]] on behalf of 
> Jamie Howarth [[log in to unmask]]
> Sent: 27 February 2016 19:18
> To: [log in to unmask]
> Subject: Re: [ARSCLIST] Cassettes that speed-up---what's up?
>
> I’ve never seen that, and i’m thinking something fairly low in frequency that was induced into the 
> head could masquerade as bias — what frequency was it? Sony dictation machines were like 43kHz and 
> that’s the best we’ve been able to see, did a job for an Atlanta outfit… The normal bias of like 
> 100kHz doesn’t survive probably because of the thermal self-noise of the head.
>
> And as I said in the post, I would more likely track the hum. which would rise in pitch on 
> playback from 60 to something like possibly 240 for a 1/4 speed slowdown. The LF recording works 
> fine regardless of how slow the tape is going. Tape can record DC.
>
> I’d love to find a mechanism that would do 15/16IPS —— anybody know of a decent quality deck that 
> will do that?
>
>
>
>
>> On Feb 26, 2016, at 8:11 PM, Ellis Burman <[log in to unmask]> wrote:
>>
>> That might be quite challenging Jamie.  I had one tape where the batteries
>> were obviously dying - the audio sped up greatly and became distorted and
>> very low level towards the end of the tape.  Once I speed corrected it (by
>> ear - just matching the voice tonality at the end with that at the
>> beginning, and then determining the middle part (linear?  or logarithmic?),
>> the bias was clearly audible in the later portion of the tape.  I guess the
>> bias frequency was very dependent on the battery voltage and dropped down
>> to well within audio range, even with the very slow tape speed.  All I can
>> say is "good luck with that one" as, at least in my case, the bias
>> frequency was not constant.
>>
>> Cheers,
>>
>> Ellis
>>
>> On Fri, Feb 26, 2016 at 9:26 AM, Jamie Howarth <[log in to unmask]> wrote:
>>
>>> Tyra - if you want them at fixed speed we can track the hum or room tone
>>> and put them back in constant natural pitch. PM me at
>>> [log in to unmask] if you like.
>>>
>>> Jamie Howarth
>>> Plangent Processes
>>>
>>>
>>> Please pardon the mispellings and occassional insane word substitution I'm
>>> on an iPhone
>>>
>>>> On Feb 26, 2016, at 11:57 AM, Tom Fine <[log in to unmask]>
>>> wrote:
>>>>
>>>> Tyra, you could have cases where the recorder batteries were low, which
>>> would cause recording speed to slow down and playback speed to increase.
>>> I've run into that with oral histories. I usually don't even try to make
>>> the result "pitch perfect." Rather, I determine a point where playback
>>> speed has gotten so fast that the intelligability has decreased badly. I
>>> then go back a bit before that, and select to the end of the field. Then I
>>> pitch-alter it for the best overall audibility, again not worrying about
>>> "perfect pitch" but rather best audibility of the words being spoken. It
>>> depends on how fast and how clearly someone is speaking.
>>>>
>>>> -- Tom Fine
>>>>
>>>> ----- Original Message ----- From: "Grant, Tyra" <[log in to unmask]>
>>>> To: <[log in to unmask]>
>>>> Sent: Friday, February 26, 2016 11:42 AM
>>>> Subject: [ARSCLIST] Cassettes that speed-up---what's up?
>>>>
>>>>
>>>>> We're transferring a collection of personal
>>> cassettes---interviews---mainly from the 90s.
>>>>> A few start out okay then slowly speed-up so people sound like The
>>> Chipmunks.
>>>>> Then, some are okay on one side but the flip side is speeded-up.
>>>>> What's up here?
>>>>> We'd appreciate recommendations re: the best way to handle these in
>>> order to get something listenable.
>>>>>
>>>>> Thanks,
>>>>> Tyra Grant
>>>>> [log in to unmask]
>>>>> 785-864-2034
>>>>> University of Kansas Libraries
>>>>>
>>>
>>
>>
>>
>> --
>> Ellis
>> [log in to unmask]
>> 818-846-5525
>
>