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By Erik Veach
There are a number of occasions in which it’s beneficial, or even necessary, to create audio stems for your song. But while one might assume that it’s as simple as bouncing and exporting all of the tracks that make up your song into individual WAVs and calling it a day, there’s actually a subtle art to deciding how you’re going to divide it all up.
So let’s explore some ways of dividing a song into different pieces and learn to appreciate the art of creating stems.
What is an audio stem?
An audio stem is a full song-length audio file that contains an isolated element, or group of elements, from the song. These stems may be groups of similar tracks, such as “drums,” “strings,” “voices,” etc. Or, they may be single instruments with all mix elements already applied. The key point is that they all need to have exactly the same length, same starting time point, and be of the same audio file type (for example: 24-bit, 48kHz WAV).
The purpose of audio stems is to allow the tracks to be inserted into any DAW and re-create exactly the same sound that you have in the original mix. This can be useful in a number of situations:
- Creating a remix
- Changing elements of the song in the future quickly without returning to the original mix session
- Sending your tracks to a mixing engineer to touch up the mix on a different DAW
- Backing up the mix
- Easily creating variations of your song, such as radio edits or instrumental versions
It’s easy to see the benefits of making audio stems for your songs, even if you may not have any immediate need for them. But to make sure we get the best use out of these stems, some care must go into the process of creating them.
As with any other art form, the best way to learn is to look at examples and develop an appreciation and an understanding of it as you start to apply these techniques yourself. So, let’s take a couple of well-known songs and decide how we might break them up into stems, as if they were our own musical creations.
Example 1: The Beatles
For our first example, let’s consider the classic Beatles song “Hello, Goodbye.”
First, we should identify what we imagine (Lennon pun intended) we might need from the stems. To save precious time and money, we certainly don’t want to look back and wish we had divided them differently yesterday (McCartney pun intended — okay I’ll stop).
Let’s suppose we want stems for three primary reasons: For stem mastering, for producing a karaoke version or altering the vocals in the future, and for our planned techno-pop remix release. With these in mind, we can listen to the song, identify all the parts present, and then categorize them into tracks that should either be kept as independent and tracks that work as a group. If you have sub-mixes already defined in your mix session, these can easily be maintained and used alone or combined with other tracks for a stem.
Often the drum tracks are sent to a sub-mix for drums, so it makes sense to create a drums stem. Ringo would be happy to hear he was the first Beatle we thought of. There is also a shaker that we should add to our drums stem, even if it’s not part of the drums sub-mix. But depending on our intended use, we may want to keep auxiliary percussion separate.
Continuing on, we might decide that the bass needs to be in its own separate stem for mastering and replacing or effecting in our techno-pop remix. The vocals should probably be divided into two stems: lead vocal and backing vocals. This way, the mastering engineer can make final EQ and level tweaks to each, plus we can easily remove the lead vocal if we want to make a karaoke version.
We’re now left with a rhythm guitar, lead guitar, piano, and orchestral strings to account for. We could split them into four separate stems, but based on our needs for these stems, it will be fine to batch the rhythm instruments all together into one stem and only separate out the lead guitar into its own stem, since it may require special attention in mastering and could have some additional fun effects applied to it for our anticipated techno-pop club remix.
Speaking of effects, we should make sure all effects from our mix are applied to every track within our stems for a full representation of the sound of the mix. As noted earlier, each stem should be exported for the full length of the song, even if the sounds only appear at certain points in the track. This will maintain proper time synchronization between all stems.
The final stems for Example 1 would then be:
- Bass guitar
- Lead vocal
- Backing vocals
- Rhythm instruments
- Lead guitar
Example 2: Pitbull and Kesha
For our second example, let’s analyze the song “Timber” by Pitbull featuring Kesha and see if we can determine a good division of audio stems.
To start, we’d need to identify what uses we may have for stems. In this case, let’s say that we’d like to have the opportunity to make a wide range of remixes, both with and without various vocal elements.
For this outcome we would want to create isolated stems of each vocalist’s work. So, let’s create a Kesha solo vocal stem and a Kesha backing vocal stem, as well as a Pitbull solo vocal stem and a Pitbull backing vocal stem. The backing vocal stems would consist of all additional vocals present while each lead vocalist is performing, including the response calls of “Timber” and the vocal ad libs appearing during Pitbull’s performances. If you’re a DJ reading this, you greatly appreciate that level of separation of elements and you’re probably already thinking about things you could do with those independent stems.
Moving along, we recognize that the song is made of percussion elements, country-rock style rhythm and lead elements, and pop synth style rhythm and filler elements. For a pop dance song like this, it’s probably best to divide the percussion into two stems: the synth bass elements and the rest of the percussion. That way they can be alternated and re-balanced in a remix version.
For the country rock elements, we can combine all the guitars and other strings into one stem and keep the prominent harmonica in its own stem for effecting or replacing in a remix version. Finally, the synth elements can be divided into two stems: the rhythm elements, such as the pads and other sounds, and the filler elements, like the risers.
So the final stems for Example 2 would then be:
- Bass beat synths
- Other percussion
- Country-rock rhythm instruments
- Synth pads, melody, and rhythm sounds
- Filler synth elements
- Kesha solo vocal
- Backing vocals during Kesha leads
- Pitbull solo vocal
- Backing vocals during Pitbull leads
It’s possible you might choose a different separation of stems than I did in these examples. While the choice is driven by needs anticipated for the stems, there is certainly a level of subjectivity to the divisions. It’s for this reason that creating audio stems should be thought of as a personal art. And, as with any other art form, the more you’re exposed to it, the more of an appreciation you gain for it, and the more you are able to voice your own personal subjective feelings and support them with examples.
I encourage you to follow this same procedure of analyzing well-known songs for how you would divide the stems. This is good practice for creating stems for your own songs. Find songs within the same genre of music as your own and imagine how you would split up the stems for different scenarios. Likely the artistic appreciation you gain from this exercise will help you with things from the perspective of your fellow collaborators, remixers, and engineers.
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Erik Veach is the owner and lead audio engineer at Crazy Daisy Productions, providing mixing, mastering, and sound editing services since 2001. He is the original pioneer of automated intelligent mastering systems, introducing them for use in professional music production in 2003.