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How to Print MIDI to Audio and Why You Should Do It

March 4, 2014

MIDI is a popular tool for music composition. In a modern music production environment, it is very common to see MIDI tracks and audio tracks living side by side in a DAW (digital audio workstation). Unlike audio tracks, MIDI tracks contain data that must be played through a virtual instrument in order to produce sound. While MIDI allows for easy manipulation of notes, velocities, and more, the downside is it always needs a virtual instrument plugin to make sound. When you’re finished composing or arranging, it’s a good idea to “print” the MIDI track to an audio track. We’ll be using Logic Pro X in this tutorial, but the core concepts are the same for every DAW.

First of all, let’s talk about the differences between a MIDI track and the resulting printed audio track.

Before Printing

Pros

  • Easy manipulation of notes, velocities, and other MIDI parameters.
  • Sound can be changed by selecting a different virtual instrument.

Cons

  • VST plugin needs to be active, resulting in increased CPU and RAM usage.
  • Depending on the VST, there might be noticeable latency.

After Printing

Pros

  • Decreased CPU and RAM usage.
  • Apply effects like any other audio track.

Cons

  • Manipulation of notes, velocities, and other MIDI parameters is not possible.
  • Can’t choose another virtual instrument to change the sound.

Creating Audio Tracks and Setting up Buses

Once your MIDI arrangement is completed, it’s time to create audio tracks to record on. For maximum flexibility, it’s best to put each instrument on its own MIDI track. This enables you to shape each instrument in the mixing stage. In the screenshot below, I have two MIDI tracks in green (Piano, Drums) and two audio tracks in blue (Piano_Print, Drums_Print). I also created an aux track (PRINT) in red. This is used to monitor the audio being recorded, but doesn’t affect anything being recorded.

In order to record audio, we’ll need to create a bridge between the green software instrument MIDI tracks and the blue audio tracks. Here’s where buses come in. By setting the output of the MIDI tracks to Bus 1, and the input of the audio tracks to Bus 1, we’ve successful created a bridge for audio to travel on. In Logic Pro X, buses are stereo entities by default (mono and stereo buses are both called Bus 1, Bus 2 etc.). In Pro Tools, buses can be either mono or stereo (Bus 1, Bus 2, Bus 1–2, etc.). This setting depends on your DAW of choice, so just keep that in mind.

Recording to Audio Tracks

Now that our bus is set up, it’s time to record some audio!

Here are two important tips to keep in mind.

  • Solo the track you want to record.
  • Always record a few more bars after the last MIDI note.

In this situation, both the piano and drum tracks are being routed through Bus 1. If we want to print the “Piano” to “Piano_Print” we have to solo “Piano”, and vice versa for the drum tracks. If we don’t do this, both the piano and drums will be recorded to both print tracks.

You’re probably thinking this now… “Why don’t I just set up a different bus for each virtual instrument, so I can record everything at once?”. While this might be a viable option for smaller virtual instruments, many modern software libraries use a substantial amount of processing power. In order to ensure the resulting printed audio tracks are free of pops and clicks, it’s best to record one track at a time.

Even though our piano and drum MIDI regions are sixteen bars long, we’ll need to record a longer region of audio in order to capture the release and reverb tail generated by the virtual instrument. Three to four extra bars is usually a good starting point.

Now solo a MIDI track and record to an audio track. You should end up with something like this…

Notice anything wrong?

The audio regions end with the MIDI regions. Notice how the release of the piano waveform is visibly cut. At first glance the drum audio might appear to be fine, but a quick listen confirms the reverb tail was not recorded. Always observe with your ears, and not your eyes!

Here’s a screenshot of the correct technique – recording four extra bars.

Now you’re free to manipulate the audio tracks however you want!

Making MIDI Tracks Inactive

After printing your MIDI tracks, be sure to deactivate them. This ensures that CPU and RAM isn’t being used in the background. The process is different for every DAW, so be sure to check documentation if you don’t know how to do this. Make sure you don’t delete the MIDI tracks in case you want to make changes to your arrangements and re-print at a later time.


Questions?

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