[speeder]

I had a music teacher that insisted analog recordings were different.

One day she said there is a simple way to prove it. Certain stringed instruments have the string move on their own to the correct note if you put them near a source of similar sound. If you put these instruments in front of a speaker playing from an analog source and have the strings move, then play the exact same music but from a digital source on the same speaker, the strings stop moving, even if to most humans it sounds exactly the same.

Sadly I never had the gear to test this, I am not a professional musician and was learning from that person as a hobby (she is a teacher for professional musicians).

[robinsonb5]

If you do ever test this, and do it rigorously (i.e. using analogue and digital versions of the same recording, with no pitch inaccuracies) you'll find the strings will resonate equally well with analogue and digital recordings, all other things (volume, tuning of the instrument, etc.) being equal.

[JdeBP]

The problem is that all other things are no longer equal, and have not been for quite some time.

Retuning digital audio to 440Hz equal temperament is an industry norm now, even for (say) re-issued 1970s stuff. You just won't get modern digital versions that are the same as the analogue versions, and the equal temperament stuff thus won't pass a resonance test unless the test instrument is also equal temperament, which most string instruments of course are not.

The far easier test for amateurs nowadays is not to buy a whole string instrument, but to use pitch monitoring applications, which all too readily show when a sound is bang-on the specific equal temperament frequencies.

Obligatory recent Fil Henley:

* https://youtube.com/watch?v=0x5dfbqE5hE

[mrandish]

Auto tune pitch correction is entirely separate from whether a properly engineered digital recording can match an analog recording to a level well beyond the ability of human biology to detect any difference in randomized, controlled, double-blinded ABX testing (https://en.wikipedia.org/wiki/ABX_test).

> The problem is that all other things are no longer equal

There are many digital recordings which have no pitch correction or other tonal manipulation applied. In those cases, all things are still equal for the purposes of the statement above.

As a separate matter, I agree auto-tune and other manipulation can be inappropriately or excessively applied, however over manipulation isn't unique to digital, it occurred in the analog era too – such as dynamic range compression and multi-band dynamic equalization. Those tools existed in tube-based, purely analog form long before digital recording became the norm and caused similar complaints when they were misapplied. There were even analog pitch correctors although they weren't nearly as flexible or precise as today's digital versions.

[0x445442]

I find this dubious since the effect she was describing is caused by resonance frequency. Since, in the example provided, the source is an amplified speaker pushing air in both cases the outcome should be the same. The more famous test of this principle is the breaking of a glass and I would be surprised if this hadn't been done with digital signal inputs.

[mrandish]

> I find this dubious

I agree. In both cases a continuously varying voltage is driving speaker cone deflection. If the voltages of two different signals vary in precisely the same way, the cone will deflect to exactly the same degree and the resulting pressure wave will generate the same resonant response from any surface it encounters. When properly implemented, today's high-end, esoteric ADC and DAC converters have insane bandwidth, frequency response and fidelity far exceeding these requirements.

Some of the confusion comes from the fact that back when consumer audio transitioned to digital and these production workflows were new, some early digital recordings were incorrectly engineered or mastered creating artifacts such as aliasing which critical listeners could hear. Some people assumed the artifacts they heard were innate to all digital audio instead of just incorrect implementation of a new technology. Even today, it's possible to screw up the fidelity of a digital master but it's rarely an issue because workflows are standardized and modern tooling has default presets based on well-validated audio science (for example: https://en.wikipedia.org/wiki/Noise_shaping#Dithering). But even in the analog era it was always a truism in audio and video engineering that "there are infinite ways to screw up a signal but only a few ways to preserve it." And it remains true today. To me, one of the best things about modern digital tooling is it's much easier to verify correctness in the signal chain.