My recorded track won’t sync

In the pandemic times many people try online music collaboration, and most people run into track synchronization issues. They’d play the backing track on one device (say, laptop) and record on another (say, phone). The recorded track would for the love of Zeus not want to synchronize with the backing track, no matter how much they dragged it left or right. It’s baffling and frustrating.

What causes this? Using two unsynchronized clocks [devices] does.

And how to do it correctly? Use one clock [device]. Make sure that that the same device plays the backing track(s) and records your performance.

Examples of setups that work:

  • A Digital Audio Workstation on a laptop or PC
  • A multitrack app on the phone (wired headphones recommended)
  • An audio recorder with the overdub function

Examples of setups that don’t work:

  • Any situation when you listen from one device and record on another.

You might think that clocks run at a constant speed, but it isn’t true. You can see it for yourself. Take any recording, about 5 minutes long, and import it into your DAW. Then play it back, and record it on your phone. Then import the recording from the phone into your DAW.

It won’t align.

It won’t align no matter how much you drag it back and forth. Either the beginning is in sync and the ending isn’t, or vice versa.

You might get away with short recordings, up to maybe 1 minute or minute and a half. They will still drift, just not enough for the drift to be perceptible.

Let’s say this represents the backing track:

A sequence of evenly spaced vertical lines on square paper.
You can imagine that lines are bar lines, or beats. Musical time.

Then you record your track on top of it, and you hope that it looks like this:

A sequence of evenly spaced vertical lines, which do not align with the grid of the squared paper.
The lines are off grid. You could drag them a little to the left and they would align again. But…

But in reality, your recorded track looks like this:

A sequence of unevenly spaced vertical lines, which also do not align with the grid.
Look closely. Lines are not spaced evenly. Even worse, the number of lines is different!

Compare it to the original:

The unevenly spaced sequence drawn next to the evenly spaced sequence. Corresponding vertical lines (number 1, number 2 and so on) are connected to show that misalignment grows to the right.
Comparison with the backing track shows that vertical lines are increasingly off grid.

How to fix this? You can’t easily fix a track that has been recorded this way. You would need to cut it into pieces and align each piece individually. I wholeheartedly advise against it. You will never be 100% sure if you aligned each piece correctly. You’ll also destroy any subtle timing properties of the recording. Maybe the musician wanted this phrase to be slightly behind the beat? It’s best to record the track again, sorry.

The solution is to record audio on the same device that plays the backing track.

It’s a subtle problem. Minuscule differences in clock speeds accumulate over time. A 0.02% imperfection in clock speed will be perceptible in a recording. You might think I’m crazy or pedantic saying that clocks of our phones and laptops are that inaccurate. But they really are! We are used to phones and laptops showing accurate time, but this is only because they synchronize time over the network. The source of accurate time is a set of atomic clocks.

If my laptop’s or phone’s clock speed is wobbly, how is it possible to ever record anything in sync? When you’re using a single device for recording, it will still speed up and slow down, but both playback and recording speed up and slow down together, and don’t drift apart.

I hope this article sheds some light on the problem, and that you see how the root of the issue is based in basic physics. I also hope I convinced you that if you want to record, you need to invest some time into learning a simple DAW, or get an audio recorder with the overdub function.