Beat Grid - help is needed

Hi there,
Apologies in advance for not knowing the correct terminology in some areas…newbie.

I’ve noticed in my learning of Mixxx that when loading some tracks into either deck, the beat grid isn’t hitting anywhere near the ‘whomp-whomp-whomp’ of a bassline. I know how to adjust the beatgrid so not a biggy, just wondering how it works.

The second thing I’m interested in is why some tracks gradually fall out of alignment with the beat grid…I’m finding this in particular with Phuture’s ‘Acid Tracks’…main bass line slips right off the beatgrid within about 8 beats of the drum and gradually gets worse until it later aligns with the beatgrid for another 8 beats or so, so I’m constantly nudging it. There are a couple of others like that. I realise that some tracks have changing BPM (L’il Louis ‘French Kiss’ I’m looking at you) which I guess would cause this, but AFAIK, Acid Tracks is a steady BPM.

Could it be something like digital files made from analogue (vinyl) sources where the turntable has slight, phonically imperceptible changes in tempo?

Thanks for any advice.

There can be a few different things going on with the beat grid.
Your guess about the analogue sources is one of them. Anything recorded on using analogue equipment can have more of a BPM “drift” do to anything from the musicians slightly changing their tempo to some peace of equipment having a slight “drag” in one spot (think a warped record) . Most modern is mostly digital and when not it is usually quantized and which means that all the song is processed by a computer to get everything to be nice and tight to the tempo. So any song that isn’t stuck to the beat by computers can have a little bit of wandering around happening.
Another thing that could be happening to you is that the beatgrid is just slightly too big or too small. For songs that the beat-grid seams to get just a little farther off for every beat that goes by, this is probably the cause. Be very careful adjusting the grid to be bigger or smaller but you can get it with patience.
Also, some songs have extra beats and missed beats or pauses. Where a portion of the song is at the same tempo but a step or two ahead or behind. With those songs, you have to decide which part is the most important to have lined up right.
I hope some of that is helpfull.

If you are using mixxx 2.3 beta it may have a problem with decoding mp3 or something else. I have found grids are right place in mixxx 2.2.3.

2.3b The grid or waveform start shifting some point of track.

This is not happening every track which has a constant tempo. Which makes it little difficult spot.

For me this is problematic because i am remixing tracks lot, using samplers and hotcues.

This issue is reported in launchpad.

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Thank you for the link

thanks everyone for the help :wink: