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音声からMIDIへ

voice-to-MIDI converter using Python

1. **Capture Audio Input**: We'll use a microphone to record the voice input.
2. **Analyze Audio**: The audio needs to be analyzed for its frequency (pitch detection).
3. **Convert Frequency to MIDI Notes**: The detected frequency can be mapped to MIDI notes.
4. **Create MIDI File**: After converting the frequencies to MIDI notes, we can save them in a `.mid` file.

We'll need some Python libraries to accomplish this:

- `sounddevice`: For recording the audio.
- `numpy` and `scipy`: For working with and analyzing audio signals.
- `mido`: To create MIDI files.
- `aubio`: For pitch detection (aubio specializes in audio-to-note detection).

### Step-by-Step Process

#### Step 1: Install the Required Libraries
First, we need to install the necessary Python libraries:

```bash
pip install sounddevice numpy scipy mido python-rtmidi aubio
```

#### Step 2: Capture Audio Input

Here’s how you can capture audio input using `sounddevice`:

```python
import sounddevice as sd
import numpy as np

def record_audio(duration, sample_rate=44100):
    print("Recording...")
    audio = sd.rec(int(duration * sample_rate), samplerate=sample_rate, channels=1, dtype='float32')
    sd.wait()  # Wait until recording is finished
    print("Recording finished.")
    return audio.flatten()
```

This function records audio from the microphone for a specified duration.

#### Step 3: Analyze Audio for Pitch (Using `aubio`)

Now, let's detect the pitch of the recorded audio using the `aubio` library:

```python
import aubio

def detect_pitch(audio, sample_rate=44100):
    pitch_detector = aubio.pitch("default", 2048, 512, sample_rate)
    pitch_detector.set_unit("Hz")
    pitch_detector.set_silence(-40)  # Adjust silence threshold if needed
    
    pitches = []
    for i in range(0, len(audio), 512):
        sample = audio[i:i + 512]
        pitch = pitch_detector(sample)[0]
        if pitch > 0:  # Only consider non-zero pitch values
            pitches.append(pitch)
    return pitches
```

This function processes the audio and detects the pitch at regular intervals.

#### Step 4: Convert Pitch to MIDI Notes

MIDI notes correspond to specific frequencies. We can map detected frequencies to their nearest MIDI note numbers:

```python
def frequency_to_midi(frequency):
    if frequency <= 0:
        return None
    midi_note = 69 + 12 * np.log2(frequency / 440.0)  # A4 = 440Hz corresponds to MIDI note 69
    return round(midi_note)
```

#### Step 5: Create a MIDI File

We can now convert the detected MIDI notes into a MIDI file using the `mido` library:

```python
from mido import MidiFile, MidiTrack, Message

def create_midi_from_pitches(pitches):
    midi_file = MidiFile()
    track = MidiTrack()
    midi_file.tracks.append(track)
    
    # Add some basic track information
    track.append(Message('program_change', program=12, time=0))
    
    # Convert each pitch to a MIDI note and add to the track
    for pitch in pitches:
        midi_note = frequency_to_midi(pitch)
        if midi_note is not None:
            track.append(Message('note_on', note=midi_note, velocity=64, time=100))
            track.append(Message('note_off', note=midi_note, velocity=64, time=200))
    
    return midi_file
```

This function takes the detected pitches, converts them to MIDI notes, and creates a MIDI file. The `note_on` and `note_off` events are added to simulate playing and releasing the note.

#### Step 6: Putting It All Together

Now, we can record audio, detect the pitch, convert it to MIDI notes, and save it as a `.mid` file:

```python
def voice_to_midi(duration):
    # Step 1: Record audio
    audio = record_audio(duration)
    
    # Step 2: Detect pitch from the recorded audio
    pitches = detect_pitch(audio)
    
    # Step 3: Create a MIDI file from the detected pitches
    midi_file = create_midi_from_pitches(pitches)
    
    # Step 4: Save the MIDI file
    midi_file.save('output.mid')
    print("MIDI file saved as 'output.mid'")

# Record and convert voice to MIDI for 5 seconds
voice_to_midi(5)
```

### Explanation:
- **Step 1**: Records audio from your microphone for the given duration.
- **Step 2**: The recorded audio is split into frames, and each frame is analyzed for its pitch.
- **Step 3**: The detected pitch is converted to a MIDI note.
- **Step 4**: A MIDI file is created with `note_on` and `note_off` events for each detected note.

### Notes:
- The code is designed for monophonic melodies (i.e., one note at a time). For polyphonic melodies (multiple notes at once), more advanced techniques are required.
- **Noise sensitivity**: Ensure that the environment is relatively quiet, as background noise can interfere with pitch detection.

This script should give you a basic starting point for voice-to-MIDI conversion in Python.

. email: [email protected]

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