pitch shifting doesn't sound good

[brownt]

Why is it that when the frequency of of musical note is changed by electronic methods, it doesn't sound good? The further the note is changed the worse it sounds. Changes in lower notes are better than changes in higher notes.

For example, playing a note on a guitar sounds ok, and playing one octave up sounds ok, but if the first note is pitch shifted an octave electronically using an effects unit, although it is up an octave it sounds different, squeaking, a bit distorted and not good. Why is that?

 

[barry]

For one thing, tt depends on how good your pitch shifter is. What algorithm do they use? Think about it. If you have a sample of a guitar note sitting in memory and play back at twice the speed, it will sound ok. A real-time pitch shifter doesn't have that luxury, it has to double the pitch on the fly. It can double the frequency of the fundamental fairly easily, but your guitar note has a bunch of harmonics as well (that's what makes a guitar sound different than a trumpet playing the same note.) It's these harmonics that get messed up.

 

[brownt]

I see. why do the harmonics get mixed up?

 

[BradtheRad]

It's true that digital speed change creates glitches, but for me these are easy to ignore in view of the convenience as I watch Youtube videos or Windows Media Player.
Digital sound processing brings extreme versatility to the table, and at low cost compared to analog methods.

There is an analog technique called heterodyning which can convert a frequency up or down by a desired ratio. It's analog, not digital. A different analog method is used in a guitar pedal effect known as an octave doubler. (Example, the Octavia invented by Roger Mayer as he worked with Jimi Hendrix in the 1960's.) Heterodyning is used in 'bat listener' devices which translate ultrasonic bat squeaks down to an audio range which we humans can hear.

 

[barry]

It's true that digital speed change creates glitches, but for me these are easy to ignore in view of the convenience as I watch Youtube videos or Windows Media Player.
Digital sound processing brings extreme versatility to the table, and at low cost compared to analog methods.

There is an analog technique called heterodyning which can convert a frequency up or down by a desired ratio. It's analog, not digital. A different analog method is used in a guitar pedal effect known as an octave doubler. (Example, the Octavia invented by Roger Mayer as he worked with Jimi Hendrix in the 1960's.) Heterodyning is used in 'bat listener' devices which translate ultrasonic bat squeaks down to an audio range which we humans can hear.

Not exactly. Heterodyning mixes two frequencies together, creating the sum and difference of the two frequencies. The only way heterodyning will work as a doubler is if the two frequencies are the same. The Octavia used a frequency doubler which, I believe, was probably a full-wave rectifier.

 

[KlausST]

Hi,

Sound pitching up is not trivial.
The problem is: you need to look into the future - which is impossible.

You can do this with a sampled record with start and end...then it's easy: to shift up one octave you just double the output frequency. But then listening to the whole record is just half of the time. .... which usually is not what you want.

But for a continous sound without start and end you need to pick a piece of input sound ... limited in time.
Do the pitching for this piece and play it.
During this play back you need to record the next piece of input sound.

This causes some problems:
* the output is delayed with respect to the input (at least by the lengh of the "piece" you record)
* the lower the frequency you want to pitch - the larger the "piece" of sound you need to pick (the bigger the delay)
* one needs to ensure a "smooth" blending from one piece to the next piece of sound to avoid "clicks" ( = glitches) at the borders.

For a good sounding pitch you need a more elaborated pitch algorithm
******

Sound:
When you play a tone at a guitar, then it has some overtones of different amplitudes.
If you play the one octave higher tone, then it also has overtones, but not with the same amplitudes the the lower tone.
This is even more true for voice - thus if you just replay voice with doubled speed you get exactly the same overtones as before ... resulting in some "unnatural" Mickey Mouse effect.
You need to decide if this is what you want or not --> different pitching algorithms.

Klaus

 

[FvM]

What kind of pitch shifting are you talking about? Is it the auto-tune or harmonizer technique that keeps the harmonic relation or simple single side band modulation that shifts all tones by a fixed frequency offset? What's the brand and model of your pitch shifting effect?

 

[Audioguru]

Seeing this thread on another forum I looked up Drake and found that him and nearly ALL other RAP and POP singers use Autotune except Christina Aguilera, even a long time ago. Links in Google show well known POP singers on recordings singing very well with Autotune then live without when they can't sing worth a damn. They showed that anybody can sing pretty well with Autotune by simply reading the lyrics.