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Comment by kazinator | Hacker News Reader

3.5% is a lot! One semitone is a bit shy of 6 percent.s

It's between 59 and 60 cents: more than a quarter semitone.

Exact value:

  1> (* 1200 (log2 1.035))
  59.5569212695205

So 59.6 to 3 sig figs. Someone with a good pitch memory of a tune (hearing in their head how it should sound) would spot such a difference. Especially if they heard the tune recently.

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So many recordings (especially before 2000) seem to be sped up a little. I can’t tell by listening to the song but when you try to play along with a guitar, it sounds terrible. Sometimes it helps to find a live version on YouTube.

Correct. That was often done when mastering with tape. Record at one speed, playback at another to make it sound more "lively." There are songs that were sped up that way anywhere from 25 to 40 cents. It's another reason why live music so often doesn't sound like the recording.

When using digital mastering, you can also adjust the playback speed, but you can correct the shift. You get more "liveliness" without the shift change. That's why you're not hearing the pitch shift so much in more recent music.

Do you happen to know of any tools for fixing pitch issues in music files?

Anatares Auto-tune.

Audacity.

Free and open-source.

I used Audacity recently to fix some youtuber's backing track for guitar improv, by tuning down 7 cents. I reuploaded it:

https://www.youtube.com/watch?v=TE3pgOkfYu0

In that case, it's a pure stretch: i.e. the tempo is slowed down by a factor of 0.996 to achieve the pitch change.

I also have an unpublished version of that track transposed from the key of Em to Dm; that was a pitch change preserving tempo.

How did you determine 7 cents was the correct amount?

Trial and error. Guitar meticulously tuned to concert pitch, with attention to the 12-15 fret area, then compare against versions of the track slowed down by all available factors in audacity from around 0.993 to 0.998. (The stretch tool doesn't take more digits, stupidly.)

"Guitar meticulously tuned to concert pitch, with attention to the 12-15 fret area"

When you need to pay attention to anything outside of open string, fretted 12th, open harmonic 12th fret (and fretted 24th if you have a 24+ fret guitar) for intonation, it's time to get the guitar to a luthier for setup maintenance. Something else is drastically wrong in the setup.

When you're deciding between a 6, 7 and 8 cent pitch shift, using your instrument as a reference, you should pay attention to the notes you are using, no matter how confident you are in the intonation.

Depends on what you're trying to do. For guitar practice, I use AnyTune Pro+. I use for learning the lead, because with my musical experience I can nail the rhythm guitar part by ear in a couple minutes. Not so with lead guitar parts, I'm afraid! But yeah, you can adjust frequency, you can adjust playback speed, you can pick a point A and a point B and loop between those points (great for breaking down each section of the solo). If you slow the playback speed slower than 70% or so, you're going to start getting a lot of digital noise. Once you've learned how to hear the notes through the noise then you can learn even super fast solos.

As I'm writing this I'm thinking to myself I know there are AI tools now that can take any track and produce all the stems for all the different parts in the track. You'd think for something like the lead guitar they could analyze that stem and produce either the tablature or standard music notation for the solo. That would be kinda awesome! I wonder if such a tool now exists?

I wrote elsewhere that I recently asked Claude AI to help me learn a Pixies song on guitar and it wouldn't give me anything but generic advice because of copyright.

I could swear the music video version of Evil by Interpol is faster than the album version, but it’s just inconvenient enough to verify that I haven’t bothered

comparing runtimes should do

What are cents in the context of playback speed? Hundredths of an RPM?

A cent is a factor of 2^(1/1200). There are 1200 cents in an octave, which is a doubling in frequency: if we have 1200 of them, 2^(1200/1200) = 2^1 = 2.

Lisp-wise:

  2> (exp2 (/ 1200))   ;; exp2 is courtesy of ISO C 99
  1.00057778950655

So, it is a .0578 percent change in pitch, or determiner of pitch like record rotations speed.

A little more intuitively, 1 semitone is one "note", aka the interval between two successive notes on a piano (including white and black keys) such as C to C#, and to talk about intervals less than that, we use cents as 1/100 of a semitone.

Musically, two notes an octave apart vary by a factor of 2 (e.g. Middle A (A4) is 440Hz and the next A (A5) is 880Hz), and our ears hear frequencies logarithmically rather than linearly, so each of the 12 semitones in an octave is a factor of 2^(1/12) higher than the previous one (so that 12 of them in a row result in doubling the frequency), and therefore the 100 cents between each semitone are each (2^(1/12))^100 = 2^(1/1200) greater than the previous one.

There are 100 cents to a semitone - by definition. The frequency shift of a 25 to 40 cent adjustment isn't likely going to be noticed by the average listener. A lot of times you don't notice it until you try to play guitar along with the song and you notice something is a little "off."

In can drive you nuts when you're playing by ear because when trying to find the root note, i.e. the key, you'll find it between two semitones. Always go for the lower tone. For example, if it sounds like it's a little sharper than A, but it's definitely not Bb, then you know it was A and the mastering was sped up. That's another thing, in my experience it's always sped up and never slowed down.

I have a theory that one of the reasons Eb standard guitar tuning started becoming so popular in the late 60s and into the 70s was because the speed up was getting to be so common that guitar players started adjusting their tuning for it, not to mention you generally get a "heavier" sound.

A bunch of the High Voltage-era AC/DC stuff was this way, IIRC. It's really awkward to play guitar along with the songs in question unless you painstakingly match the goofy tuning of the song, or adjust the pitch of the song first.

Same with This Charming Man by The Smiths and Mary Jane's Last Dance by Tom Petty

Oh man. Love Tom Petty. RIP.

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