Possibly strange question - Why do some of my tracks act weird when changing the tempo in DJ software

[Barfunkel]

Something strange I noticed a long time ago but never put any thought into it - until now. Basically, when I load (some of) my tracks into DJ'ing sofware (the free Mixxx in this case) and move the tempo slider even slightly, I get these strange artifacts. I absolutely never get them with any commercial releases.

Whether it is wav, mp3 or whatever, it doesn't matter. They don't happen when I select vinyl-style pitching which doesn't timestrech, but with timestretching on, the artifacts can be loud and very, very annoying. And it's only with my own tracks, not with anything else.

Is this a symptom of something being wrong in my productions, a strange bug in Reaper's rendering algorithms or what?

Here's an audio example. First it's at the original BPM 129, then I change the tempo to about 131 and you can clearly hear the artifacts.

[Ben Kohonays]

That's bizarre.

I don't have an answer, but you could rule out Reaper's rendering algorithms by importing a commercial track and rendering it to see if it does the same maybe.

[ozias_leduc]

Is your song mastered? I wonder if those transient smearing artefacts are more likely with non-smashed tracks

But you can always tell when, for example, Ableton DJs are mixing with algorithms other than "re-pitch" because you do get those weird artefacts

[Plyphon]

If you want, you can send me that track and I can try the same through serato - to rule out your DJ software.

[Barfunkel]

If you want, you can send me that track and I can try the same through serato - to rule out your DJ software.

I can do that, but it's strange that the software doesn't have artifacts with commercially released music, just my own. The one in the SC link is the most blatant example, usually it's a more tolerable and not always even audible with casual listening.

[Lost to the Void]

Mastering issue I expect.

[henry1]

Mastering issue I expect.

Mastering can be a culprit behind some issues encountered with DJ software?
This is can be a very serious problem.

Could you help elaborate how that could be?

[Lost to the Void]

Once you master stuff, dance music in particular. A lot of the work is smoothing, rounding and smearing transients, and in general glueing the mix together.

Stretching hose transients with an algorithm becomes less noticeable.

Sharp brief transients and peaks in an uncontrolled premaster (or a badly limited one) are going to show more artefacts when you stretch them out.

Highly dynamic acoustic recordings never sound good in stretch algorithms.

[henry1]

Very insightful, thanks.

Better hope those labels master professionally.
No need for paranoia.