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Audio to MIDI Recorder (Version 4.0)

Audio to MIDI Recorder converts audio into MIDI data that can be streamed to control networked devices in real time, or recorded and shared. Polyphonic pitch detection algorithms operate on live or pre-recorded music (iTunes). Algorithm settings optimize performance for voice or instrumental music.

Sound Examples

The first example is a flute to electric guitar transcription of a part of Bach's Partita in A minor.

The second example uses the app to drive a synth that plays along with Oscar Peterson's "Brotherhood of Man" with Clark Terry.

How to Use

The top toolbar lets you select either "Live" music and sounds picked up by the device's built in microphone, any song from your iPod library ("iTunes"). After a brief conversion delay (which depends on the length of the song), tap the play button to start the song.

The app starts up ready to record instrumental music. You must change settings to record voice (see below). Adjusting the top slider changes the input level in "Live" mode. Sing or play into the device and adjust the slider until the pitch detector triggers. The detected note is displayed at the top. Detected notes are displayed in "piano roll" format. Tap "Start" to begin recording, and "Stop" to end.

After recording tap "Play" to play back the recorded MIDI notes, and "Stop" to end. The file is played continuously using built in sounds at a fixed volume and velocity.

Tap the action button at the bottom right to email the current recording. The recorded file contains MIDI pitch and velocity information.

Tap the gear icon to reveal a table of settings. Audio to MIDI Recorder uses several types of pitch detector. "0 db (voice)" is for recoding solo voice; "3 db", "6 db", and "9 db" are for instrumental music. Different combinations of detectors (e.g., filter banks, correlators, etc.) are invoked depending on the signal to noise ratio. There are seven performance ranges:

  • Full range (C2-C7)
  • Whistling (C5-C7)
  • Soprano (C4-C6)
  • Mezzo-soprano (A3-B5)
  • Alto (F3-F5)
  • Tenor (C3-C5)
  • Baritone (F2-F4)
  • Bass (E2-E4)
The last section of the table sets what we call "Polyphony", which is the maximum number of new notes that can be triggered at a time. Some experimentation is required to determine the best settings for your application. In almost every case MIDI recordings will have to be edited to remove extra notes, add notes that were missed, and adjust note timings.

Controlling Other Devices

Besides recording, Audio to MIDI Recorder continuously transmits MIDI pitch, velocity, and channel volume to networked devices. If you use this with other Midi apps, Midi Bridge or a similar app is required to route Midi signals between apps. Follow the directions below for wireless control of networked computers.


Download a wireless MIDI interface such as DSMidiWifi and install on your computer. Launch Audio to MIDI Recorder on your iOS device. Connect your device's MIDI stream to the synthesizers you want to control. For example, on a Mac use Audio MIDI Setup to connect your iPhone/iPod Touch to Garage Band or other MIDI units networked to your computer. Turn on Garage Band or other MIDI synths. Launch Audio MIDI Setup, select MIDI, and click on the network icon. You should see this screen:

Select your device and click Connect. As you sing or play into the device the bar graph will show the network latency.


Be sure to install the latest version of iTunes, which contains Bonjour for Windows. Then install rtpMIDI, which is available free at: rtpMIDI on the PC looks and functions like Audio MIDI Setup on the Mac. rtpMIDI will detect your device when Audio to MIDI Recorder is running. Start a new session in rtpMIDI and then you will be able to select the session as a MIDI input device from within your DAW or other MIDI setup.

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