_DK said:
Is there a way to tell a master tape reel (i.e. a 30 year old 7 1/2 ips reel with a live soundboard recording from 70s) from a digital source recording on an old tape? One person has offered me to buy a tape like that, and I said that I'll pass...but what if it was a real one?
And my other similar question was: are there any techniques of finding out if a tape is a master or a copy of a master? Because I've got some of my friends master tapes from early 90s and some are copies. They're not labeled and he obviously doesn't remember which is which. I know that the general rule is to pick the better sounding tape, but they sound the same to me or my ear could be not as good. Should I compare the output frequencies? Any better way of doing that?
This has been an area in forensic science for many years, relating to whether an evidence tape is an original or the evidence within it has been edited and copied to distort the truth etc. The only way to edit it is to make an edited copy of course, so establishing if it is a copy can be very important to its value as a piece of evidence.
Repeated and careful listening should usually tell which is the copy. But from my experience, some people dont hear differences unless they are really obvious.
The extra distortions that are likely to be in a copy :
Increase in harmonic distortion, tape hiss, and tape dropout (instantaneous reductions in output) are obvious ones. Intermodulation distortion is where one frequency, such as a bass guitar, "modulates" the rest of the mix so that the mix "vibrates" or gurgles in time with the bass's fundamental frequency. Often a compression of the dynamic range due to tape saturation on the copy, usually accompanied by the increase in harmonic distortion.
Another is azimuth error. Especially if the source tape was replayed/copied from another machine, rather than the one it was recorded on, there may be a reduction of high frequencies but also a "drifting" effect where the highs and even the mids are not true and there's a kind of "comb filter effect" where only certain frequencies are reduced. A bit like with a vocalist singing into a mic off axis.
An increase in wow and/or flutter, meaning slow or fast variations in the speed and tempo, often very minor.
Sometimes also there's the presence, or just an increase, in mains hum. If there was hum on the original, you sometimes get a doppler effect (beats, pulsing) between that hum and any introduced hum from the copy machine.
It's important that the machine you replay the tapes on is also a high quality
type and in very good condition. Otherwise the faults or incompatibilities in that machine may so compromise the audio as to blur any audible difference between the two taped versions. Ideally the machine's play head azimuth should be carefully adjusted to the actual recording's azimuth pattern. Equally that the tapes' track configuration be established eg: half track, quarter track, full track and the tape played on the appropriate machine. Otherwise the fidelity will be compromised.
Obviously the monitoring amps/speakers/headphones should be of good quality.
Just a general but not necessarily huge reduction in fidelity is what you are looking for.
A good example in a commercial recording is the classic 1966 Beach Boys "Pet Sounds" re-release CD which unusually has on the one CD both the original release master tape version and a new remix which goes back to the multitrack tapes from which the mono master was made. Even though the newer remix is in stereo while the original release master is mono, it's not too hard to detect in the mono version:
more tape dropout, tape hiss, intermodulation distortion, noticeably the bass line of the rest of the mix, and even, on the first track "Wouldnt it be nice", a mains hum, just in the quiet introduction.
Pet Sounds won huge praise on the strength of the mono version which is a copy or a copy of a copy. Today we can hear it clearer and in stereo simply because the original tracking tapes survived.
You seem to be suggesting someone might have made a digital copy of a recording, copied it onto an old reel to reel tape and tried to pass it off as an authentic original recording. That might be hard to tell unless you have something to compare it with. I'd be listening to the tape for signs of an old recording that wasnt totally erased and that might give some clue as to whether the recording is genuine or not.
If the recordings are at all valuable they should be treated carefully. Later 70's tapes may have sticky shed problems and if so probably shouldnt even be played before checking them for this and possibly baking them as per standard procedure. We could point you to more information on this.
If unsure, the safest way may be to put the tapes in the hands of someone who does this work all the time, such as Richard Hess. Just Google in that name and you should find him.
my 2 cents' worth.
Tim
I'll pay more attention to the things you've pointed out.