tempo shift using sample rate adjust?

[Mark Lemaire]

Hi! It's been a while since I've been here.

I have a 96/24 multitrack project where the tempo is a bit too peppy. I'd like to knock it back a small amount without ruining the sound. Thoughts?

BTW- under "Formats and Sync" there is "Varispeed". I have tried this, (moving from "nominal' to 'varispeed'), and it will not accept anything more dramatic than moving from '1000' to '1001". This makes no difference that I can hear to the tempo. I'd like to try a bigger shift, but cannot get PMX to accept anything more than this.

Your thoughts are welcome!

[J.Waterhouse]

Have you tried using ZTX pro? If you have any version of Pyramix higher than Native essentials I believe you should have it as one of the rendering options. It gives you quite precise control when time stretching or pitch shifting. If you're wanting to do a dramatic shift in pitch it will let you do this, though it will be worth adjusting the quality and localization slider to try and get the most transparent end result - obviously a bigger shift in pitch will leave more audible artefacts. Of course, rendering would mean you'd lose control of any edits you've done so maybe this isn't an option in this case.

Potentially there's also the Resampler, which you can see in Media Manager if you right click on a file and choose "quick convert" then "Resampler".

Apart from those two options, the next best thing might be to use something else outside of Pyramix. For example, my RME interface allows you to bend the sample rate/pitch of things, though I've never actually used this feature so I'm not entirely sure it would suit your purpose. I think it would be possible to run a mix through it at a given specific sample rate/shift and record it back in.

[Mark Lemaire]

Thank you. I’m actually not looking for pitch shifting. I’m looking for a tempo shift. Does the very speed control ring any bells with you? Let me know your thoughts. The ZTX pro sounded kind of gummy when I tried it

[fl]

Mark,

First off, the absolutely best method of shifting pitch OR tempo, is to re-record. Anything else involves a greater or lesser degree of audible imperfection.

Pitch Shifting and Tempo Shifting are basically the same thing, and are based on re-sampling. If you use the varispeed control for your RME interface, you're actually changing the sample-rate, such that a recording made originally at 96 kHz SR, now plays at 95,900 Hz, for example. This is great for short term listening, but if you wish to incorporate this into your project for release in a standardized format, you have to find some way of getting things back to the "standard" sample-rate, while simultaneously maintaining your shifted tempo. Slowing the tempo in this way also lowers the pitch in much the same way an analog tape recorder would if you were to play the tape back slower or faster, and people have been doing this for decades - you might remember Alvin and the Chipmunks. Recording at a slower speed and then playing back normally, yields higher pitches but that 'chipmunky" sound, and you might consider this as an option in a recording session for when your singer just can't hit that high note. Doing the opposite by recording at a higher speed, yields a clogged, nasal sound, but slight errors become magnified, and with singers can result in an unacceptably slow vibrato. But with this method, you can't have one without the other - pitch and time are inextricably linked, unless you have some technological means of separating them, and all that that entails.

Now there are programs which can adjust tempo in a different way - Melodyne comes to mind, as does "Beat Detective" in ProTools. These essentially chop up your audio into many separate sections, and then allows you to space them closer together or further apart, either manually, one by one - which is monumentally tedious - or by lining everything up according to some sort of tempo map. In Pyramix and most other DAWs this can be quite sophisticated, but in a lot of popular dance music, this usually means a rigid, metronomic beat structure, because it's easy, and dancers seem to like it.

ZTX provides the first sort of shifting, combining the shifting with automatic resampling to the original SR. As you have discovered, shifting things beyond a certain range - say, a semitone or so - you start to hear artifacts. What might be acceptable for a short amount of time - say, for correcting a single bad note - is not when applied to a complete piece.

I have used the Pyramix's Resampler to adjust complete recordings, such as the time I did an a cappella vocal group whose pitch centre would drift over the duration of a piece. I found that when we recorded an insert Take starting at some point in the middle of the piece, they would tune to the "proper" pitch, which unfortunately was not the pitch at that same point in the music when they had done a complete Take. No amount of futzing around in the Cross-fade Editor could disguise a shift of even a few cents, which would immediately catch your ear and scream, "EDIT!". I was able to resample the insert takes so that their pitch lined up with their corresponding position in the full take, and just lived with the slight change in tempo. I found that this gave me better results with fewer artifacts. What you'd want to do is more or less the same, but to adjust the tempo in this way, you'll have to live with the slowed down timbre change in the performance, unless you can find some glitch-free software solution that causes fewer artifacts.

For your project, where the tempo is to "peppy", I think you can't avoid using some kind of re-sampling - either Pyramix's, or with a pitch/tempo adjustment program, such as the conveniently built-in ZTX, or one of the many other pieces of stand-alone software which allow you to change tempo without altering pitch. A cursory web-search for "pitch/tempo software" came up with many suggestions, including some which are free of charge. If you already own Izotope RX, you've got one right there, which has the added feature that you can vary the amount of shift over time, gradually raising or lowering the pitch and/or tempo according to a user drawn contour on a time vs. pitch (or tempo) graph.

[phaseboy]

Just a few thoughts from my experiences.

ZTXPro is not bad for small adjustments of short sections. I will regularly use this when editing if a few bars I'm inserting are a slightly different tempo that the surrounding material, and it doesn't feel right without some correction. For a long section or an entire piece I find I am rarely happy with the results and find that I prefer iZotopes Radius algorithm (which is also licensed by Avid and is available in Pro-Tools as X-Form (nb: the elastic audio x-form is not the same thing)). In the rare instances where I want to adjust a complete piece or a something that is really dense and complex I will often render the audio and process it offline

Best regards,

Mark

[charlienyc]

...I prefer iZotopes Radius algorithm (which is also licensed by Avid and is available in Pro-Tools as X-Form (nb: the elastic audio x-form is not the same thing)).

As Frank mentioned, this is built into Rx, at least Rx7 Advanced.


It's hard not to sound like a iZotope fan around here. It's really useful stuff.

[Mark Lemaire]

Thank you everybody! I will not be able to try out your solutions until the end of the month. But I will keep them in mind and refer to this page when the time comes. Thanks again.