Phase vocoders

[Dave2002]

Phase vocoders have been pointed out (see Recorders thread) as a means of changing pitch while retaining timing, and to some extent the envelope of a sound.

Here are some possibly useful/interesting articles about these -

http://anasynth.ircam.fr/home/english/software/supervp

https://cycling74.com/tutorials/the-phase-vocoder-%E2%80%93-part-i

https://en.m.wikipedia.org/wiki/Phase_vocoder

https://www.panix.com/%7Ejens/pvoc-dolson.par

https://web.archive.org/web/20040617224423/http://www.ircam.fr/equipes/analyse-synthese/roebel/paper/dafx2003.pdf

While these techniques can be used for recorded music in offline mode, what I'd like to know is if they can also be used in real time in online mode - i.e. for live shows. There would be some buffering delay in the circuits/software, but depending on the size of windows, buffers etc. and the quality desired, it might (but only "might") be possible to get this down to a few milliseconds. Delays longer than (say) 10 milliseconds would probably not be very useful/helpful. Longer delays may improve the quality of the results, but would probably be pointless for live shows.

Software systems are/have been available - see http://www.soundhack.com/
and Spear is another - see the link in http://www.iu.edu/~emusic/courses/K504/assign3.htm

I don't know if these two systems are currently viable.

[MrGongGong]

What do you want to do?

Pitch changing is simple and widespread
Spectral manipulation is also simple

Mr Norris is the man

http://www.michaelnorris.info/software/soundmagic-spectral

Using some of this tomorrow to play flugelhorn into creating drones for Indian singing etc

[Dave2002]

OK - is the delay with this software perceptible? Perhaps not.

I’ll try the download - thanks for that. I’ll report back in a while - probably not today. Currently watching tennis.

[Dave2002]

SoundMagic Spectral requires Mac OS X 10.6 or later. An AudioUnit-compatible host, such as Logic, Performer, Live, Amadeus, Sound Studio, or Max/MSP using my au~ object, is needed.

This looks like a plug-in or set of. Does it/they work with Reaper, or many other DAWs? I'm expecting a "yes" answer, but I don't want to go off on a wild goose chase if it's going to be very fussy. Might even work with some of the ones you dislike most, perhaps!

Here is a section on AudioUnits:

Audio Units allows sound file audio time stretching and pitch scaling (e.g., timestretch), sample rate conversion, and streaming over a Local Area Network. It also comes with a set of AU plug-ins such as EQ filters, dynamic processors, delay, reverb, and a Soundbank Synthesizer Instrument.

AU are used by Apple applications such as GarageBand, Soundtrack Pro, Logic Express, Logic Pro, Logic Pro X, Final Cut Pro, MainStage and most 3rd party audio software developed for macOS such as Ableton Live, Amadeus Pro, Ardour, Audio Hijack, DaVinci Resolve, Digital Performer, REAPER, and Studio One.

so looks as though should work with a lot of MacOS software.

https://en.wikipedia.org/wiki/Audio_Units

[MrGongGong]

This looks like a plug-in or set of. Does it/they work with Reaper, or many other DAWs? I'm expecting a "yes" answer, but I don't want to go off on a wild goose chase if it's going to be very fussy. Might even work with some of the ones you dislike most, perhaps!

Here is a section on AudioUnits:

so looks as though should work with a lot of MacOS software.

https://en.wikipedia.org/wiki/Audio_Units

Yes, these work with lots of DAW's etc (even Logic and so on ...)

You obviously can't "Timstretch" a sound in "real time" BUT you can manipulate the spectrum ... Spectral Gate and Hold being one of my faves.

[Dave2002]

Yes, these work with lots of DAW's etc (even Logic and so on ...)

You obviously can't "Timstretch" a sound in "real time" BUT you can manipulate the spectrum ... Spectral Gate and Hold being one of my faves.

Agreed. However, can you do dynamic pitch changes?

[MrGongGong]

Agreed. However, can you do dynamic pitch changes?

What do you mean by "dynamic" pitch changes?

[Dave2002]

Ok - I imagine sitting in a room with a microphone, playing an instrument. The microphone is connected to a phase vocoder and the output is fed to an amp+speaker in another room. The sounds in the other room are at a different pitch, and the delays are minimal.

Another option is to do everything in one room, and try to minimise feedback by suitable mic and speaker placement. In the case of a one octave shift down, problems - if any - might be minimal because of the harmonic relation between the original and shifted pitches.

[Richard Barrett]

Ok - I imagine sitting in a room with a microphone, playing an instrument. The microphone is connected to a phase vocoder and the output is fed to an amp+speaker in another room. The sounds in the other room are at a different pitch, and the delays are minimal.

No real reason why it has to be in another room, unless that's part of your concept. Real time pitch shifting has been around for some time; I used it in a piece for electric guitar 20 years ago, with one of these https://digitech.com/en/products/whammy-5th-gen (as you'll see, used by many luminaries of the electric guitar world). Nowadays of course there are very many plugins for DAWs which will do similar things much more accurately (that is to say in a way that isn't optimised for electric guitars). Once more, putting in a minute or two on your favourite internet search engine will yield enlightening results.

[Dave2002]

Thanks for this. Is this an area which will have been missed by many “classical” musicians, with the emphasis on being able to play instruments well, either as soloists or in orchestras? Perhaps singers are also unaware of this technology - though I bet some aren’t. Years ago I heard a radio programme with a record producer/engineer who said that he’d quite often tweak the tuning of performers who hadn’t got it quite right after the nth take - so no need for the Marni Nixon’s of this world now, then!

Some artists may have an objection to technology “on principle” - as indeed do I to a certain extent - but clearly there are occasions when it can be very useful.

Doing some of these modifications live - in real time - is an interesting way to go, and I didn’t know it was really possible.

PS: Are most of the pitch shift hardware units (such as your Whammy) aimed at guitarists, or are there some more general ones which could work with other instruments or voices? Guitars may have complex waveforms which would tend to mask any peculiar artefacts, this making the results more acceptable. For very pure sounds these units might not work so well.

[MrGongGong]

\Once more, putting in a minute or two on your favourite internet search engine will yield enlightening results.

I'm not sure that Dave has the same internet as we do ?

http://www.synthtopia.com

https://monoskop.org/images/2/21/Wishart_Trevor_On_Sonic_Art.pdf

https://www.gearslutz.com/board/

and so on and so on and so on .......

(you should have come to todays gig in Dewsbury, i was doing a heap of this kind of stuff live with Flugelhorn etc )

[MrGongGong]

Some artists may have an objection to technology “on principle” - as indeed do I to a certain extent - but clearly there are occasions when it can be very useful.

.

I know what you mean
The piano is a terrible invention, music was ruined by its introduction

[Richard Barrett]

Years ago I heard a radio programme with a record producer/engineer who said that he’d quite often tweak the tuning of performers who hadn’t got it quite right after the nth take

Autotune is used for probably 90% of pop vocals these days.

Guitar effects pedals are aimed at guitarists, yes.

Real-time application of digital pitch shifting to instruments and/or voices is fairly commonplace in contemporary music. There are hundreds of ways of doing it, some of which are as "realistic" as you can imagine (including shifting the formant structure of a vocal so that a woman's voice transposed down takes on the sound quality of a man's voice).

I didn’t know it was really possible.

You need to get out more (or for that matter stay in), and hear what people are actually doing!

[Dave2002]

I'm not sure that Dave has the same internet as we do ?

http://www.synthtopia.com

https://monoskop.org/images/2/21/Wishart_Trevor_On_Sonic_Art.pdf

https://www.gearslutz.com/board/

and so on and so on and so on .......

(you should have come to todays gig in Dewsbury, i was doing a heap of this kind of stuff live with Flugelhorn etc )

I know about gearslutz ....

Did you record your gig? Dewsbury a bit far away - plus I didn't know about it until very recently.

Plus today I spent commisioning a robot lawnmower - only cut through its wires a couple of times ....

[Dave2002]

Distortions ....

My main interest in these originally was in simulating the sound of a deeper instrument with a higher one - in my case a bass (basset) recorder with either a soprano or a treble. I also looked at real time gadgets, such as electric guitarists use.

I noted that for the guitar that pitch shifters are used, but that for more complex music - with chords - it seems that some form of "harmony" gadget is preferred - though I don't really know what the differences would be.

I tried deliberately pitch shifting a few mp3 recordings down an octave. One was of Brahms' cradle song, with a soprano and piano, and the other was also of Brahms - but orchestral - one of the Hungarian Dances. In both cases the music is still recognisable. However, the words of the song are impossible to make out, and the orchestral music does sound very processed. Part of the interest here was to see if results on music with different melodic strands would be better (?? or at least more quickly/easily) done by recording each strand separately, then pitch shifting, then merging all together - or if it would be possible to do the merge (overdubbing) first, then the pitch shift. I think both methods should work, but the results will probably be horrible in either case!

Intelligibility of words is completely mangled with an octave shift and other instruments playing. Maybe small (semitone or tone) shifts - perhaps with less complex accompaniments - would retain most of the intelligibility. I've not tried that yet.

There may be uses for these devices, and some people may like the distorted sound that they can produce. I'm not ruling these out completely as potentially useful tools, and others may like to experiment. For my part I'd probably want to use them (if at all) with as little obvious distortion as possible. On some instruments the added distortion might still be acceptable for pitch shifting, and I'd still like to try a unit which can do this more or less in real time.