The Track Gap in the 21st Century – sequencing your albums right today

Nota Bene: I’d like to encourage all readers who have somehow dealt with the issue described here in any way or made experiences otherwise to share them with me and the readers here! Thanks!

Today, I’m dealing with track spacing on digital releases – which you may get from iTunes, bandcamp, or archive.org, and which you might listen to streaming or from a local file, on your computer, on your smartphone, or on whichever other device.

But how does the track spacing – the time between two tracks – work on these platforms? How do you have to proceed as the person responsible for the track spacing in the album production – artist, producer, mastering engineer, or a combination of any of these, to ensure the resulting album is just like you intended it artistically? I decided to find out…

The Old Formats

Looking at audio distribution formats of the past – if we don’t look to far into the past, this would amount to vinyl records (LP for albums), CD and various tape formats. All of them have one thing in common: the audio is contained here as some kind of audio stream: meaning, you get a defined sequence of “audio events” in the order and in the same timing relationship (and, unless you “detune” your turntable or tape deck, also abolute timing) as on the master.

This is at first completely independent of the concept of tracks – of single titles located in that stream. A tape deck does not care if the artist intended the first ten minutes as one track or as three short tracks with a pause of two seconds in between; it will play back the exact sequence of audio input that was put onto the tape. The same is true for a vinyl record and also (with some technical details I don’t want to discuss here) for a CD.

Now where did those track gaps come from? They were an artistic decision of course, by whichever party responsible for that in the production process. In the classical world, this is typically the choice of the performer. In rock and pop music, this can be any of the artist, the producer or the mastering engineer. The choice here differs with the nature of music: concept albums of any kind tend to have the artist in a responsible role here, with the producer and the mastering engineer merely offering advice, while on a “collection of songs” pop album, the artist often couldn’t care less, and the producer might leave the choice to the mastering engineer.

No matter the technological or artistic differences: For all of these old formats, the creator of the album had to make decisions on that, and those decisions were then reproduced at playback on every device and at every time in the same way.

And another one (and this is the important one): For albums where the track spacing played an important role, the creator was able to ensure the listener experienced the track spacing the same way the artist had intended it.

Digital Albums

Digital albums today (typically) appear as a collection of individual audio files, corresponding to the track concept of the legacy formats. The difference to those legacy formats is that the collection of single tracks that forms the album is no longer a continuous audio stream, rather a collection of individual audio streams which are then played in the correct sequence by your media player.

Let us try to show how this concept would work in the world of CDs: the concept of the digital album with multiple files corresponds to you getting your album as a set of single-track CD singles, which you can then place in a CD changer and instruct it to play them in sequence.
Now with a CD changer, there’s differences between different models in the way they’re made, and also for a specific model differences in the time they take to change from disc 1 to 2 than from disc 10 to 1, for example – all that meaning that the playback device now adds an additional time amount between each track, and this time amount differs from player to player and sometimes even for the same player.

So how far is that relevant for digital albums?

Quite simple: a media player playing back your digital album is similar to that CD changer playing back a set of one-track CDs. It will most probably not take the same time to cue up the next track as your CD changer, it may not even need any time at all, but – and that’s the important one – the technological concept behind the digital album does not ensure proper and reproducable playback of track spacing the same way the old formats did.

So how long does a player take to switch from one track to the next? I decided to do some field measurements.

Measurements

What I did:

First, I created a kind of pseudo-album made up of test tracks. Each one of those contained five seconds of a sine wave. Five seconds to be not so short that the tracks influence each other (and I hope that is the case here).

Then, these were put onto various media playback devices. I imported them into my Windows Media Player library, put them onto my portable MP3 player, created a hidden album on bandcamp and also put them into a player on my website.

Finally, I would play back the album, record the playback, and then use an audio editor to measure the resulting track gap.

Note here that the tracks themselves had no silence in them – so a media player which played them back in strict sequence without adding gaps would have a resulting track gap of zero.

I thus arrived at a total of eight measurements per device (five album tracks, played twice).

Not that I did consciously NOT try to optimize any system setup on the computers for that goal, nor did I use a huge number of different hardware and software setups. The idea here was which kind of numbers we’re looking at here in typical user configurations.

Results

Sony NWZ-S616F

A simple, portable MP3 player. Results were 342/343ms seven times, and 306ms one time. That means that one time it took more than 10% shorter than usual. Relatively reproduceable, albeit the absolute time is more than 10% of a standard CD track pause (2 seconds).

Windows Media Player/Windows XP 32/Lenovo ThinkPad X121e

25ms, and 26ms once. Very short, and very reproduceable. Even though it will result in a slight click if you put the track gap in the middle of a tune, it perfectly works with “silent” pauses.

Bandcamp/Chrome/Windows XP 32/Lenovo ThinkPad X121e

An average of 1459ms, with times ranging between 418 and 2219ms rather wildly. Not only is that pause in the same order of magnitude as a standard CD pause (and thus, may be too long for an intended rather short pause, also for “mainstream” applications), the main problem is the wide range this lands at. If on a properly produced album the pause is meant to be 2.2 seconds and it ends up 400ms (or vice versa), this is not good.

MP3jplayer/Chrome/Windows XP 32/Lenovo ThinkPad X121e

A plugin for wordpress, running on my moinlabs webserver. An average of 195ms, with times ranging between 130 and 469ms (the latter being a +125% of the average!).

And the Conclusion…

Unfortunately, there is no defined relationship between the creator’s intention and the listener experience regarding the track gap for digital albums.

The situation is relatively cool for “everything local”: if you’re playing back an album you have downloaded, either on the computer or on another device (MP3 player, smart phone), the measurements suggest that the resulting track gaps are, if not comparable on an absolute scale, then at least reproducible for a specific device.

Things look grim, however, for online playback, at least for the services considered here: the times vary widely, and that is no surprise, as this has to do with so many effects down the line from the media server all the way to your computer.

As a summary: a properly spaced concept album does not work for online playback on the normal systems, and only to a limited extent for single-file-based digital distribution. The solution? I don’t know…

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