Introduction to MIDI and Computer Music:  Mixing Down

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Mixing Down

The final stage of your electronic music-making process is an audio CD or MP3 file. To make either of these, you need to produce a stereo mix file — a stereo sound file that contains a mix-down of your entire Digital Performer project.

This discussion assumes that your sequence has at least one audio track, a MIDI track that plays the Korg, a MIDI track that plays a Reason device, and an Aux track that receives the audio generated by Reason.

The mix-down process consists of several stages:

Capturing Korg Tracks as Audio

You must capture the sound made by the Korg and store it as a soundbite in an audio track. To record the Korg audio output into Digital Performer, use these instructions from Exercise 3:

You may find that the audio version of Korg sound happens slightly later than the MIDI version. This is due to latency — the delay between the time that the Korg plays a note and the time that the sound of the note is recorded by Digital Performer. For percussive tracks where it's easy to hear a difference, you should move your soundbite to a slightly earlier point in time. You can play the original MIDI track and the new audio track at the same time to decide if there's a noticeable delay. If a soundbite starts at the beginning of a track, how do you move it earlier? First you have to edge-edit it to move its left boundary further to the right. Then zoom in and drag the soundbite to the left, or use the Edit > Shift command.

Capturing Reason Tracks as Audio

To play Reason sounds from Digital Performer, you need at least one Aux track, which brings into Digital Performer the audio Reason generates, and zero or more MIDI tracks, which send MIDI messages to Reason. (Setting this up was the subject of Exercise 2.) To make a stereo mix-down file, you first need to capture the Reason audio as one or more soundbites. Here's how to do it.

  1. Create a new stereo audio track in DP (Project > Add Track > Stereo Audio Track).
  2. Set its INPUT column to Reason:Mix L 1-Mix R 2.

  3. Record-enable this new audio track.
  4. Press the Record button.

    The sound Reason makes when you play your sequence will be recorded into the new stereo audio track.

  5. Mute the original Reason MIDI and aux tracks, so that they don't make sound while you play the sequence. Their sound is now contained in the new audio track.

Capturing Nanosampler Tracks as Audio

  1. Select a time range for both the nanosampler Instrument track and the MIDI track that contains notes played by the nanosampler.

  2. Choose Audio > Freeze Selected Tracks.
Digital Performer will play the sequence and record audio from the nanosampler into a new audio track that it creates in your Track List. Then you should mute the MIDI and Instrument tracks you had selected. You no longer want to play these, because the audio they generate is now contained in the soundbite on the new audio track.

Adjusting Your Mix

At this point, you've captured your Korg and Reason tracks as audio tracks in Digital Performer. Now you have to mix them down to a single stereo audio track.

  1. Disable playback of all tracks except for audio tracks.
  2. Adjust the volume of the audio track that contains Korg sound so that it matches the level you were used to hearing before you captured the Korg MIDI track as audio. The audio track might sound too soft. If you've turned up its volume fader to the maximum (+6 dB), then you can get more level by using the Trim effect on that track in the Mixing Board. However, if you really need to resort to this, it's probably better to re-record your Korg audio.

    The Reason audio track should have the same level that you've been hearing while working on your sequence.

  3. Make sure that your sequence doesn't clip when you play it. In our case, clipping means that the amplitude of the waveform sent to your headphones exceeds the range of a 16-bit integer. This creates distortion. Clipping can be caused by the mixing of individual audio tracks whose volumes are too high, or by certain audio effects that can create high amplitude peaks.

    You should turn individual track volumes down until they no longer clip. If they don't sound loud enough to you, you can use the Masterworks Limiter effect to reduce the dynamic range of the track, which raises the apparent volume of the track without clipping. Just choose this effect in the Mixing Board, and turn down its Threshold knob a little bit.

    You can also clip at the main output where all the tracks are mixed together. Normally, there's no meter that tells you when this is happening. The best way to guard against this sort of clipping is to use a Master Fader track. Create one by choosing Project > Add Track > Master Fader Track. This track holds no soundbites. It merely gives you a single volume fader that controls all of your audio tracks together. Adjust this fader while playing your sequence so that the meter for the Master Fader track, shown in the Mixing Board window, never turns red.

Bouncing to Disk

  1. Make certain all audio track outputs are set to Built-in Output 1-2.
  2. Select all the audio tracks you want to include in your mix file. Shift-click the track names in the Tracks window to select them. You don't have to include the Master Fader track in the selection.
  3. Your audio tracks and the Master Fader track must be play-enabled.
  4. Use the Start and End time boxes in the Tracks Window to select the time range you want to capture. Usually, you'll want the entire length of your sequence, plus a few extra empty measures to accommodate any reverb or echo ring-off. (A shortcut: to select the entire sequence duration, double-click on the word "Selection" that appears to the left of the Start and End time boxes.)

  5. Choose Bounce to Disk from the Audio menu. Use the following settings in the dialog that appears.

    Press the Choose Folder button, click on Desktop, and press Choose, so that the mix file will end up on the Desktop.

    Press OK in the Bounce To Disk dialog. Another dialog will pop up, but you can just OK it.

Making an MP3 File

To find out how to convert your interleaved stereo mix file into an MP3 file, read these instructions.

©2006, John Gibson