Convert MIDI to MP3 or WAV with Audacity: A Comprehensive Guide

Have you ever found yourself with a MIDI file that you wanted to listen to on your phone or share with a friend who doesn’t have a MIDI player? MIDI files, while excellent for storing musical information, aren’t audio files themselves. They need to be rendered into a format like MP3 or WAV to be directly playable. Thankfully, with the free and open-source audio editor Audacity, you can easily convert your MIDI files into these common audio formats. This comprehensive guide will walk you through the entire process, step-by-step, ensuring you can get your MIDI music into the format you need.

Understanding MIDI and Audio Files

Before we dive into the conversion process, it’s crucial to understand the difference between MIDI and audio files.

• MIDI (Musical Instrument Digital Interface): MIDI files are essentially instructions for musical instruments. They contain information about which notes to play, when to play them, how loudly, and which instrument to use. They’re not actual recordings of sounds but rather commands that a synthesizer (software or hardware) interprets to produce music.
• Audio Files (MP3, WAV): Audio files, on the other hand, store actual sound recordings. MP3 is a compressed audio format, which means it takes up less storage space but may lose some audio quality. WAV is an uncompressed format, preserving all of the audio information but resulting in larger file sizes.

Therefore, converting a MIDI to an MP3 or WAV isn’t a simple file format change. It involves taking the MIDI instructions, having a synthesizer interpret them, and then recording that interpreted audio output into a new audio file.

Why Use Audacity for MIDI Conversion?

Audacity is a powerful and versatile audio editor, making it an excellent choice for converting MIDI to audio. Here’s why:

• Free and Open Source: Audacity is completely free to use and modify, making it accessible to everyone.
• Cross-Platform: It works seamlessly on Windows, macOS, and Linux operating systems.
• Versatile: While not specifically a MIDI editor, Audacity can record audio input, which is the key to capturing the sound produced by a MIDI synthesizer.
• User-Friendly: Although it has many advanced features, Audacity’s interface is generally intuitive and easy to learn.
• Extensive Format Support: It can export audio files in a variety of formats, including MP3 and WAV.

Prerequisites

Before we begin, make sure you have the following:

1. Audacity: Download and install the latest version of Audacity from its official website (https://www.audacityteam.org/).
2. A MIDI Synthesizer: This is the software that interprets the MIDI data and produces sound. You can use:
   • A Software Synthesizer (VSTi): These are often plugins that run within a Digital Audio Workstation (DAW). Popular options include Synth1 (free), Serum, Massive, etc. You don’t *need* a DAW for this process, but if you have a DAW, it can be the easiest solution as they often have robust MIDI synth capabilities.
   • A Built-in Synthesizer: Most operating systems have a built-in synthesizer, often accessible through MIDI-compatible software. On Windows this may use the Microsoft GS Wavetable Synth.

   For this guide we will use a windows native solution, but this process would be largely the same if you used a vst based solution.

3. A MIDI File (.mid or .midi): The MIDI file you want to convert.
4. Soundflower or similar (macOS) / Loopback (macOS) / WASAPI Loopback (Windows): These are virtual audio cables which allows you to direct the sound from one application (your MIDI synthesizer) to another application (Audacity). On Windows, you can use the built-in WASAPI loopback function and do not need additional software. On MacOs you may need to install soundflower or loopback which cost money. This guide will focus on using the Windows WASAPI method.

Step-by-Step Guide: Converting MIDI to MP3/WAV with Audacity on Windows

Now, let’s dive into the actual conversion process. We will use the windows WASAPI loopback method. If you are on Mac or have another setup this will be similar but will require slightly different steps.

Step 1: Configure Audacity for Recording

1. Launch Audacity: Open the Audacity application on your computer.
2. Select the Recording Device: In Audacity, locate the microphone dropdown menu (usually near the top left of the interface). This is the device Audacity will record from. Change this to `Windows WASAPI`.
3. Select the Audio Source: To the right of the microphone dropdown is another menu. In this menu choose what input device you want to use for your recording. Change this to your default sound output device (e.g. Speakers or Headphones).
4. Select Audio Channels: To the right of the input source menu, there is a dropdown which sets the number of recording channels. Select `Stereo recording Channels`.

Step 2: Play Your MIDI File with Your MIDI Synthesizer.

You will need a program that can play MIDI files. Windows can play these natively if you double-click on a MIDI file and your default audio will be the microsoft GS wavetable synth. This does not support very many instruments and the sounds are of low quality. We recommend finding an external software synthesizer.

In this example we will use the native microsoft GS wavetable synth.

1. Open your MIDI file: Locate the .mid or .midi file on your computer, and double click on it. Your default midi player should open and begin playing. Make note of the software that is playing the MIDI data as you will need to not close this software while recording with audacity.

Step 3: Record the Audio in Audacity

1. Prepare to record: Place the window of your MIDI player and Audacity so you can easily click between them.
2. Start Recording: In Audacity, click the red Record button (or press ‘R’ on your keyboard). Audacity will begin capturing the audio output from your system sound output, which is your playing midi file.
3. Start playing your MIDI: Immediately after clicking the record button in audacity, start playing your MIDI. Ensure it plays through to the end to ensure you get all of it.
4. Stop Recording: Once the MIDI file has finished playing, click the black Stop button in Audacity (or press the space bar). The waveform of your recording will now appear in the Audacity window.
5. Trim the Recording: You might find that there’s some extra silence at the beginning or end of the recording. You can trim this by:
   1. Select the unwanted section by dragging your mouse over it.
   2. Press the Delete key to remove the selected audio.

Step 4: Fine Tune the Recording (Optional)

At this point you have a raw recording of your MIDI audio. If you would like, you can optionally clean up your audio further:

• Adjust Volume: If your recording is too quiet or too loud, you can adjust the gain using the gain slider next to the microphone dropdown. If your file peaks and becomes distorted you will need to re-record with a lower gain setting.
• Noise Reduction: If you notice any background noise, use the Noise Reduction tool under Effects > Noise Reduction to remove or lessen background noise.
• Other effects Audacity offers a wide range of tools in the Effects menu to further refine the audio you recorded.

Step 5: Export the Audio as MP3 or WAV

1. Select the export file format: Click on the `File` menu, and select `Export`. Choose either `Export as MP3` or `Export as WAV` depending on your needs.
2. Choose a File Name and Location: In the export dialog, give your new audio file a name and specify where you want to save it on your computer. If you selected to export to MP3 you can also set the quality of the export here.
3. Export the Audio: Click the `Save` button to export your MIDI audio as an MP3 or WAV file.

Tips for Better MIDI Conversions

• Choose a Good MIDI Synthesizer: The sound quality of your converted audio depends heavily on the synthesizer you use. Experiment with different synthesizers to find the best sound. Software synthesizers, particularly VST instruments, often offer a wider range of higher-quality sounds compared to built-in options. You will get the best sound out of VST’s.
• Record at the Right Level: Before recording, make sure the output volume is at a good level in your MIDI synthesizer. Avoid recording at very high or very low volumes, as this may cause distortion or quiet audio. Check to make sure the output is not peaking (hitting 0.0db), this may cause distortion.
• Isolate Your Recording Environment: Close other applications that might produce sound notifications or system noises. This can ensure that only the MIDI audio will be recorded, giving a clean, professional result.
• Experiment with Editing: Audacity is a powerful audio editor. Use its tools to fine-tune your recording. You can use these tools to fix any problems you have with your file.
• Consider Export Options Depending on what you are doing with your audio, consider what settings to use for the export. For music listening MP3 is often prefered, however if you are further editing the audio or for critical listening WAV is prefered.

Troubleshooting Common Issues

• No Audio Being Recorded:
  • Double-check that you have correctly selected the WASAPI loopback method and the appropriate input device in Audacity.
  • Ensure that the MIDI player is playing audio and that your default audio output is working correctly.
  • If your sound is playing through another device, such as headphones instead of speakers, you will need to select that device as your WASAPI input.
• Poor Audio Quality:
  • Try using a different MIDI synthesizer. Some synthesizers have better sound quality than others.
  • Check the volume of your MIDI player. High output volume may cause the signal to be distorted, and it may need to be lowered before recording.
  • Ensure the export quality is set to high. This may increase file size, but also will increase sound quality.
• Background Noise:
  • Make sure that no other applications are producing sounds and that you do not have any other noise sources in your room.
  • Use Audacity’s noise reduction tool to remove any persistent noise from your recording.

Conclusion

Converting MIDI files to audio formats like MP3 or WAV with Audacity can be a little tricky at first, but with this detailed guide, you should now be able to complete the process successfully. By correctly configuring Audacity, using a good MIDI synthesizer, and following the steps outlined above, you can easily convert your MIDI files into high-quality audio files for listening on various devices or further audio production. Remember to explore the additional features and effects that Audacity provides to further enhance your converted audio.

Experiment with different synthesizers, settings, and effects to find what works best for your particular needs. Happy music making!