Time stretching at mastering stage: common practice or nonsense?

Hey guys,

I have been considered to master a hip-hop album and I am about to get the first track as a sample before the artist and I reach a final agreement. I am only a beginner at mastering.

The artist requests that the track is sped up 2 bpm. My initial reaction is that this will lead to noticeable digital artefacts and I am inclined to strongly discourage this, but it might be a common practice that I am not aware of? I am not familiar with producing hip hop music.

Any opinion on this?

I’ve never had access to time stretching algos that sound good enough to use on a master.

But, I read that on David Gilmour’s “On an Island” solo album, when the final mixes were delivered they decided the album was a little too laid back so they sped tracks up marginally, trying several different algorithms to find the one that was most transparent.

I know it’s a very different kind of music but the principle’s the same…

Here’s the SOS article; https://www.soundonsound.com/people/recording-david-gilmours-island

Here’s the relevant part;

"One of the things Chris felt is that a lot of the tempos were too slow. It’s a fairly laid-back album anyway, completely overtly so, and David’s never been apologetic about that. He said ‘That’s where my head’s at, that’s what I want to do.’ But Chris still felt some of the tracks were too slow so we ended up, after a lot of experimentation, time-compressing some things using Serato Pitch 'n Time in Pro Tools, which is generally regarded as being the best-sounding time-manipulation plug-in out there. The time-compression was a very laborious process, but fortunately somebody else did it — listening to each part, deciding which algorithm worked best for which type of material! This was all done on a second Pro Tools rig in another room.

"There were a few things Serato didn’t do so well, but we got round it. For example, it really messed up the kick drum — it added some kind of backwards echo — so we just took some of the uncompressed ones and replaced them manually, lining them up in the waveform display. That didn’t take as long as you might think — maybe half an hour to an hour per song. It also enabled us to find a good loud one, a good quiet one, which suited Chris as he likes the kicks to be consistent and well behaved. It worked fine and it didn’t end up sounding like a drum kit made of bits.


I’d simply do it and bill them for it of course. I wouldn’t fight them on this. If it damages the track, its their own damn fault. They may not notice the difference in the artifacts. I don’t know shit about mastering, but I have a real hard time seeing a client that would make a noob request like that nit picking at the artifacts it creates. Especially a hip-hopper.


If they are asking for it, just explain what some of the downsides might be if you do it. Then do it and show it to them. If it sounds terrible, then explain it and see if they agree. I suspect it actually won’t sound that bad. Just make sure you use a good pitch shifting algorithm, because they vary in quality a lot, and different algorithms sound better on some sources than others.

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I don’t suppose you can tell them they might be better off having it done to the mix before you master it? (master of the obvious)


Boz, these guys are rappers. I wouldn’t bother attempting to explain this.

I’d do it, get paid, then show it to them.

I don’t think it’ll sound terrible unless @Lophophora majorly screws up the settings time stretching in the DAW…I wouldn’t explain this, I’d strait up tell them “Yeah! Good call…I think this sounds great. You feeling it?”

I’ve never met a rapper who could tell his head from is ass on something like this.

Miked, I think the simpler solution would be to speed up in the mastering…seems it would be a lot easier than trying to speed up every single vocal clip in the session in order to remix 2 bpm faster. All the non-midi stuff would get nudged out of time.


I thought you could just select all the tracks and time stretch them… Done. I guess not. (?)

Ha. Good point.

Yeah, just do it because it’s what he asked. Make it sound as good as you can because that’s your job. And move on. Trying to attach ideologies of what mastering should or shouldn’t be is counter-productive.

Ah. I see what you’re saying.

Yeah, theoretically that might work better. Because time stretching algorithms (like Abletons for example) tend to act different based on if your source is percussive, monophonic, polyphonic etc…

I guess you could bill for more time if you did that…good idea.

2 BPM shouldn’t be that significant (depending on the tempo of the song). It is worth a shot. Depending on if you hear artifacts you can treat each one as a repair. You may be surprised. Most DAWS are steadily improving their time stretching algorithms. Logics has improved quite a bit in the last couple years. It is almost getting useable for drum edits:)

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Thanks for your input guys. I told him that I could do it for an additional price but that it might result in some digital artefacts. He decided not to go with it.

Looks like @Jonathan loves hip-hoppers! :grin:

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In principle I agree, however, the overriding principle must be your reputation, and that is built on any and every recording that has been through your hands. “Crikey this sounds shit, who mastered it?” “Jonathan” “Well, I know who won’t be mastering MY album, then.”

My initial reaction is don’t touch it with a barge pole. If they wanted it 2 bpm faster they should have recorded it 2bpm faster. It’s like opening a massive can of worms that could come back to bite you on the arse at any point in the future. I would be extremely reluctant to even discuss it, let alone attempt it.

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I agree and that was my initial reaction. However, this would be one of my very first mastering client, I am willing to pay out some slack so I can build a portfolio :wink:

Good point.

I wonder if this conversation actually ever comes up. If it sounds so bad that people are going to recognize the poor quality, then it’s also probably bad enough that nobody is every going to listen to it. Bad music has this really great feature built into it that nobody hears it.

So unless you are advertising it on your site, and it sounds bad, nobody is ever going to attach your name to it. It’s fine to not do things because you don’t think it sounds good, but don’t pretend that it’s because it will do anything to your reputation, because it won’t unless you are advertising with it.


Umm… I’m not pretending. It’s a principle: make sure that your work is shit hot if you want repeat business and recommendations. If your principle is: don’t worry if your work is shit because no-one listens to shit stuff anyway, that’s cool, but I prefer my own, because it actually works for me.

These are both good points, and I don’t think there’s a correct and incorrect here…mainly because business ideology is as subjective a mix itself. AJ, I would say the in a market you’re trying to break into and make impressions in, CLA would say ‘make sure nothing leaves unless it sounds radio ready, even the rough mixes’. He would argue that ‘you never know who’s gonna hear it’.

On the flip side, I’d say remember that these are rappers. Amateur rappers. There’s also the question of weather a 2bpm time stretch is gonna mean a hill of beans when it comes to impact of the finished thing. If its an imperfect mix, but the client is happy and the consumer base by large can’t identify the flaws, I don’t know if you can really say it hurts anything. I don’t know how it works in the UK where you are or (in Singapore?) where Lophophore is, but in the Southeast US, rappers have the lowest standards of any style I can think of.

I think the principle AJ alludes to here is valid. That the client, even of the lowest standard, still impacts your reputation at first. I’m having to cater to the lowest denominator in the film world because I’m trying to get established. And like running a restaurant, consistency of services and consistency of product is quite important.

May I point out that without hearing that master, we may all be speculating way beyond what’s practical and overthinking this a bit?

As I said, the question is now irrelevant because the guy has decided not to go with the time stretching.

In Singapore the music industry is seriously under-developed (considering the high reputation the country has in other areas like finance, hi-tech etc). There few recording studios and producing businesses, and even the most established don’t seem to be able to meet the quality standards we know in Europe and North America. I wouldn’t even try selling mastering services in my home country (France), where I know I wouldn’t be able to reach the professional standards there. I’m saying this so you might better understand the context in which I’m working in.

I’m currently finishing this master, taking my time with long breaks between sessions so I can assess the tonal balance with fresh ears and play it in a variety of environments. I’ll upload it here so you can give me your feedback (which will be greatly appreciated) if you’re curious.

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Oops! I didn’t see this. I didn’t backtrack far enough in the thread before responding lol.

India is the same way. And I couldn’t even begin to hypothesize why. I realize that India is huge and immensely diverse, but from what I’ve heard of and heard about the pop music over there, its quiet behind the times as far as pushing the envelope with production technique. Its crazy how avid’s primary tech support call center is in Singapore…and until you get into their high-end commercial product line, you almost deal exclusively with Singapore locals for licensing and software activation issues. Even basic PT and Sibelius and Media Composer issues are handled in Singapore. I wouldn’t say its bad, but you’d think they’d find the best support teams in the areas which are most music technology sophisticated. But that doesn’t seem to matter. Crazy stuff!

It doesn’t take musical technology sophistication to tell people they can’t uncheck the “install plugins” box if they want the plugins installed. 90% of support can be taken care of by someone who doesn’t know what a guitar is.