Pitch-Shifting makes sample sound out of tune

2

I recorded a guitar sample using a seemingly in tune guitar, and the raw sample sounds in tune also. However, when I pitch shift the sample down by EXACTLY 400 cents (using FL Studios built-in pitch shifter) to get a sample that should be 4 semitones lower, the resulting sample sounds out-of-tune.

Can anyone explain why this happens, and if there are any better pitch shifting methods I could be using?

I've bounced a quick comparison of the original and pitch shifted sample playing one after the other, with an in-synth accompanying:

https://soundcloud.com/fakelion/tuningissue/s-cXnNd

Any help is much appreciated!

nobosity

Posted 2016-06-16T00:28:34.767

Reputation: 133

As far as I can tell, the pitch-shifting is being done by the elastique plugin – nobosity – 2016-06-16T00:56:06.623

Curious. It doesn't sound out of tune to me. What are the notes in the chord? I hear the root and a ninth, and am having trouble making out the inner notes (if there are more than two notes in the sample). Does it sound sharp or flat to you? Are you taking into consideration that pitch shifting the chord implies a tonal modulation (i.e., a different scale)? – Phil Freihofner – 2016-06-16T01:20:19.203

It is quite subtle, but the second chord is definitely ever-so-slightly flat. The notes being played on the guitar are E-A-D-G-B-A (l-h, essentially a strummed bar chord), with the synth playing an Em11, so the tonality is exactly what was expected (4 semitones down to a Cm11) but it sounds like someone magically detuned the guitar playing the sample after the pitch shift! – nobosity – 2016-06-16T01:34:16.117

It is a very small tuning issue, but I was wondering if there was any reason (differing sample rate etc.) why an in-tune sample would go slightly out-of-tune after a precise pitch change – nobosity – 2016-06-16T01:35:37.053

1Sometimes a guitar is tuned in a way that makes intervals more perfect rather than equal-tempered. Moving a just-tempered chord to a different key could give a sense of the second chord being out of tune relative to the first. (Just a thought.) I think to really test whether the pitch-shifting is accurate, you should isolate a single note and test it with a tuner. It was hard for me to distinguish what was guitar and what was synth on your recording. Maybe separate them right/left? – Phil Freihofner – 2016-06-16T02:17:08.690

3Just had another thought. The pitch shifting will change the timbre, making the second chord sound duller than the first. All the harmonics in the tone color also are brought down. Perhaps this makes the result sound "flat"? – Phil Freihofner – 2016-06-16T02:23:58.780

I'm pretty sure you're right about the timbre change - I pitch shifted the same sample up instead of down and it had the opposite effect! Thanks for the advice! – nobosity – 2016-06-16T16:26:32.220

Answers

2

I am no expert, but could your guitar have been tuned to Just temperament, instead of Equal temperament?

Correct me if I am wrong, but if one tunes the guitar by the ear, it does not necessarily sound completely in-tune from all chords? One does need to use tuning meters to check nice tuning against equal temperament instruments (like pianos or more importantly, digitally "perfectly" tuned synths).

This is a complex subject, You could spend ages with it.

but, to get some sort of intro, please browse (read) through these articles:

http://www.guyguitars.com/eng/handbook/Tuning/temperament.html http://www.phy.mtu.edu/~suits/scales.html

If you hear that pitch shifted sample is a bit flat, compensate it by shifting a bit more (or less) than 400 cents. As according to Wikipedia, human ear recognizes about 5 cent steps.

I am sure, that someone playing in a band - tuning their guitars against the band member's instruments, can give You even beter lowdown on this subject.

Mikko Sundman

Posted 2016-06-16T00:28:34.767

Reputation: 31