🎹 Raspberry Pi MIDI Looper

A hardware-based 10-track MIDI looper pedal built with Raspberry Pi 3B+ and designed for use with Casio keyboards. Record, layer, and loop MIDI performances with physical button controls and LED feedback.

✨ Features

10 Independent Tracks - Layer multiple MIDI recordings
Super Looper Mode - Perfect synchronization with fixed loop duration
Backing Track Recording - Hear previous tracks while recording new ones
Auto-Looping Playback - Tracks loop seamlessly based on longest recording
Full MIDI Capture - Records velocity, sustain pedal, and all MIDI CC data
Multitrack Tone Isolation - Each track can use a different instrument/tone
Persistent Storage - Auto-saves session, survives power cycles
MIDI Export - Export as merged or separate MIDI files
MIDI Import - Load existing MIDI files into tracks
Visual Feedback - LED indicators for mode, tracks, and recording status
Tone-Independent - Recordings play in any sound you select on your keyboard

Here is a quick video https://github.com/user-attachments/assets/2e4bd62a-28d7-422f-b661-94d50daeed41

🛠️ Hardware Requirements

Components

Raspberry Pi 3B+ (1GB RAM)
Casio CTX870IN Keyboard (or compatible USB-MIDI keyboard)
4× Tactile Push Buttons
1× Touch Sensor (TTP223 or similar)
10× Green LEDs (Track indicators)
1× Red LED (Recording mode)
1× Yellow LED (Playing mode)
1× Blue LED (Pause indicator)
1× White LED (Clear track indicator)
1× Red LED (Delete all indicator)
Breadboard & Jumper Wires
USB Cable (USB-A to USB-B for Casio keyboard)
Power Supply (5V 2.5A+ Micro USB)

Optional

Resistors (220Ω) for LEDs (code uses PWM at 20% duty cycle as workaround)

📐 Pin Connections (BCM Numbering)

Buttons (Pull-Up, connect to GND)

Component	GPIO Pin	Physical Pin
Button 1 (Mode Toggle)	GPIO 5	Pin 29
Button 2 (Start/Stop)	GPIO 6	Pin 31
Button 3 (Left/Pause)	GPIO 13	Pin 33
Button 4 (Right/Clear)	GPIO 19	Pin 35

Touch Sensor (Active High)

Component	GPIO Pin	Physical Pin
Touch Sensor OUT	GPIO 26	Pin 37
Touch Sensor VCC	3.3V	Pin 1 or 17
Touch Sensor GND	GND	Any GND pin

Status LEDs (Anode to GPIO, Cathode to GND)

LED Color/Function	GPIO Pin	Physical Pin
RED (Recording Mode)	GPIO 20	Pin 38
YELLOW (Playing Mode)	GPIO 21	Pin 40
BLUE (Pause)	GPIO 22	Pin 15
WHITE (Clear Track)	GPIO 23	Pin 16
RED (Delete All)	GPIO 24	Pin 18

Track LEDs (Green, Anode to GPIO, Cathode to GND)

Track	GPIO Pin	Physical Pin
Track 1	GPIO 4	Pin 7
Track 2	GPIO 17	Pin 11
Track 3	GPIO 27	Pin 13
Track 4	GPIO 25	Pin 22
Track 5	GPIO 12	Pin 32
Track 6	GPIO 16	Pin 36
Track 7	GPIO 2	Pin 3
Track 8	GPIO 3	Pin 5
Track 9	GPIO 8	Pin 24
Track 10	GPIO 7	Pin 26

Ground Distribution

Connect all LED cathodes and button grounds to GND pins:

Pin 6, 9, 14, 20, 25, 30, 34, 39 (all are GND)

🎛️ Button Functions

Button 1: Mode Toggle (GPIO 5)

Recording Mode ↔ Playing Mode

Only works when STOPPED (not during recording/playback)
Visual indicator: RED LED (REC) / YELLOW LED (PLAY)

Button 2: Start/Stop (GPIO 6)

Master transport control

When Stopped in REC Mode:

Starts recording on currently selected track
Overwrites previous recording on that track
Backing tracks (other recorded tracks) loop in background
RED LED and selected track LED blink during recording

When Stopped in PLAY Mode:

Plays all recorded tracks together
Tracks loop automatically based on longest track duration
All tracks with recordings light up

When Running:

Stops recording/playback
Sends MIDI panic (stops stuck notes)
Auto-saves session (in REC mode)

Button 3: Left/Pause (GPIO 13)

Context-sensitive dual function

When Stopped in REC Mode:

Navigate LEFT through tracks (10 → 9 → 8 → ... → 1 → 10)
Selected track LED lights up
Use to choose which track to record on

When Playing in PLAY Mode:

PAUSE/RESUME playback
BLUE LED lights when paused
Sends MIDI panic when pausing

Button 4: Right/Clear (GPIO 19)

Context-sensitive dual function

When Stopped in REC Mode:

Navigate RIGHT through tracks (1 → 2 → 3 → ... → 10 → 1)
Selected track LED lights up
Use to choose which track to record on

When Playing in PLAY Mode:

CLEAR currently selected track
WHITE LED flashes briefly
Track immediately goes silent
Session auto-saves

Touch Sensor: Delete All (GPIO 26)

Emergency reset

Deletes ALL 10 tracks permanently
Stops playback/recording if running
Sends MIDI panic
RED "Delete All" LED flashes for 1 second
⚠️ No undo!

💾 Software Features

Auto-Save System

Auto-saves after each recording in REC mode
Auto-saves when tracks are cleared
Auto-loads last session on startup
Dual session files:
- Normal mode: ~/looper_autosave/session.json
- Super Looper mode: ~/looper_autosave/supersession.json
Survives power cycles!

CLI Commands

Access via SSH to control advanced features:

# Super Looper Mode
SL ON              # Enable Super Looper with fixed duration
SL OFF             # Return to Normal mode

# Track Status
status             # Show all tracks, durations, and mode

# MIDI Export
save               # Export tracks (merged or separate)

# MIDI Import
load <track> <file.mid>   # Load MIDI file into track

MIDI Export

Export your compositions via SSH:

save

# Choose option:
# 1 - Merge all tracks into one MIDI file
# 2 - Export each track as separate MIDI files

# Files saved to: ~/looper_exports/

Merged export: merged_output.mid (all tracks combined)
Separate exports: track_1.mid, track_2.mid, etc.

MIDI Import

Load existing MIDI files into tracks:

# Syntax: load <track_number> <filepath>
load 1 ~/my_melody.mid
load 5 /home/pi/Downloads/bass_line.mid

Track Status

Check which tracks have recordings:

status

# Normal mode output:
# Mode: Normal
# Track 1: 245 events, 8.32s
# Track 2: Empty
# Track 3: 189 events, 5.47s
# Longest track: 8.32s

# Super Looper mode output:
# Mode: 🔒 SUPER LOOPER (Fixed Duration: 8.50s)
# Track 1: 245 events, 8.50s (forced to SL duration)
# Track 2: 189 events, 8.50s (forced to SL duration)
# All tracks loop to: 8.50s

🚀 Installation

1. Flash Raspberry Pi OS

Use Raspberry Pi OS Lite (64-bit)
Enable SSH in imager settings
Configure WiFi credentials
Set hostname: raspberrypi
Username: pi

2. Install Dependencies

# SSH into Pi
ssh pi@raspberrypi.local

# Update system
sudo apt update
sudo apt upgrade -y

# Install required packages
sudo apt install -y python3-pip python3-rpi.gpio python3-mido python3-rtmidi

# Or if apt doesn't have them:
pip3 install --break-system-packages mido python-rtmidi

3. Upload Looper Script

# On your Mac, copy the script to Pi:
scp looper.py pi@raspberrypi.local:~/

# Or create it directly on Pi:
ssh pi@raspberrypi.local
nano looper.py
# Paste the code, save with Ctrl+X, Y, Enter

4. Test Manually

# Make sure Casio is plugged in via USB
python3 looper.py

# You should see:
# Found Inputs: ['Casio USB-MIDI...']
# System Ready.

# Press Ctrl+C to stop

5. Enable Auto-Start (Optional)

sudo nano /etc/systemd/system/looper.service

Paste this:

[Unit]
Description=MIDI Looper
After=network.target

[Service]
Type=simple
User=pi
WorkingDirectory=/home/pi
ExecStart=/usr/bin/python3 /home/pi/looper.py
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target

Enable it:

sudo systemctl enable looper.service
sudo systemctl start looper.service

# Check status:
sudo systemctl status looper.service

📁 File Transfer (Mac ↔ Pi)

From Mac to Pi

# Copy file to Pi's home directory:
scp /path/to/file.mid pi@raspberrypi.local:~/

# Copy to specific location:
scp melody.mid pi@raspberrypi.local:~/looper_exports/

From Pi to Mac

# Copy file from Pi to current directory:
scp pi@raspberrypi.local:~/looper_exports/merged_output.mid .

# Copy multiple files:
scp pi@raspberrypi.local:~/looper_exports/*.mid ~/Desktop/

Using SFTP (Alternative)

# Connect with SFTP:
sftp pi@raspberrypi.local

# SFTP commands:
get looper_exports/merged_output.mid  # Download
put my_track.mid                      # Upload
ls                                    # List files
cd looper_exports                     # Change directory
exit                                  # Quit

🔒 Super Looper Mode

Super Looper Mode ensures perfect synchronization across all tracks by enforcing a fixed loop duration. Unlike normal mode where tracks loop at different lengths, Super Looper guarantees all tracks align to the same timeline.

Key Features

Fixed Duration Enforcement - All tracks loop to the exact same duration
Perfect Synchronization - No drift or timing misalignment between tracks
Separate Session Management - Independent save files for Super Looper and Normal modes
Auto-Stop Recording - Recordings automatically stop at the set duration limit
Two Setup Methods:
- Manual Declaration: Set a specific duration before recording (e.g., 8 seconds)
- First Track Duration: Use the first recorded track's length as the fixed duration

Activating Super Looper Mode

Via the CLI (SSH into your Pi):

# Enable Super Looper
SL ON

# You'll be prompted to choose setup method:
# 1. Declare time manually - Enter duration in seconds
# 2. Get time from first recorded track - Duration set automatically

Example session:

SL ON

=== Super Looper Duration Setup ===
1. Declare time manually
2. Get time from first recorded track
Choose option (1/2): 1
Enter duration in seconds: 8.5
✓ Super Looper enabled with 8.50s fixed duration

Using Super Looper Mode

Manual Duration Setup:
- Type SL ON
- Choose option 1
- Enter duration (e.g., 8 for 8 seconds)
- All tracks will now loop to exactly 8 seconds
- Recordings auto-stop at 8 seconds
First Track Duration:
- Type SL ON
- Choose option 2
- Record your first track normally
- When you press Stop, that duration becomes the fixed length
- All subsequent tracks loop to this duration

Recording Behavior

Shorter than Fixed Duration:

Fixed duration: 8.00s
Recorded:       5.50s
Result:         Track loops twice (2.5 loops per cycle) to fill 8.00s

Exceeds Fixed Duration:

Fixed duration: 8.00s
Recorded:       9.20s
Result:         Track cut at 8.00s, ⚠️ warning displayed

Deactivating Super Looper Mode

# Return to Normal mode
SL OFF

# Your Super Looper session is saved
# Normal mode session is restored

Session Management

Super Looper uses separate session files:

Super Looper: ~/looper_autosave/supersession.json
Normal Mode: ~/looper_autosave/session.json

Switching modes:

Current session is auto-saved
Mode switches to new mode
Previous session in that mode is loaded
All tracks and settings are preserved independently

Checking Status

status

# Output in Super Looper mode:
# Mode: 🔒 SUPER LOOPER (Fixed Duration: 8.50s)
# Track 1: 245 events, 8.50s (forced to SL duration)
# Track 2: 189 events, 8.50s (forced to SL duration)
# All tracks loop to: 8.50s

When to Use Super Looper

✅ Best for:

Drum patterns and rhythmic loops
EDM/electronic music production
Perfectly timed backing tracks
Songs requiring strict timekeeping

❌ Not ideal for:

Free-form improvisation
Varying phrase lengths
Classical/jazz with rubato

🎼 Multitrack Usage Guide

Understanding Track Channels

Each track uses its own dedicated MIDI channel (0-9) for tone isolation:

Track 1 → Channel 0
Track 2 → Channel 1
...
Track 10 → Channel 9

This means every track can have a different tone/instrument simultaneously!

Recording Multiple Tracks with Different Tones

Workflow:

Select tone on your Casio keyboard before recording
Press Button 2 to start recording
The tone is automatically captured and saved with the track
Navigate to next track (Button 4)
Change tone on keyboard
Record next track with new tone

Example:

Track 1: Select "Grand Piano" → Record melody
Track 2: Select "Strings" → Record harmony
Track 3: Select "Bass" → Record bass line
Track 4: Select "Drums" → Record percussion

Backing Track Recording

When recording a new track, all previously recorded tracks play in the background:

Hear the complete mix while adding new parts
Perfect for layering complementary melodies
No need for external metronome if you have a rhythm track

Example:

1. Record drums on Track 1
2. Select Track 2 → drums play as backing track
3. Record bass while hearing drums
4. Select Track 3 → drums + bass play as backing tracks
5. Record melody with full rhythm section

Looping Behavior

Normal Mode:

Each track loops at its own recorded duration
Shorter tracks loop multiple times per cycle
Example: 4s track + 8s track → 4s track plays twice

Super Looper Mode:

All tracks loop to the same fixed duration
Ensures perfect synchronization
Example: All tracks loop to exactly 8.00s

Tone Independence

Your recordings store MIDI data only, not audio:

Change tone on keyboard anytime during playback
All tracks respond to new tone selection
Example: Record in Piano, play back as Strings

Per-Track Tones (Advanced): The system remembers each track's original tone:

Track 1: Piano (Program 0)
Track 2: Strings (Program 48)
Each plays with its recorded tone during multitrack playback

Track Management

Clearing Individual Tracks:

1. Switch to PLAY mode (Button 1)
2. Start playback (Button 2)
3. Navigate to track to clear (Button 3/4)
4. Press Button 4 (Clear) - WHITE LED flashes
5. Track immediately goes silent

Clearing All Tracks:

Touch the touch sensor
→ RED LED flashes for 1 second
→ All 10 tracks deleted
→ ⚠️ No undo!

MIDI Export Options

Merged Export (Single file):

save
Choose: 1
# Creates: merged_output.mid (all tracks combined)
# Use in: DAW software, MIDI players

Separate Export (Individual files):

save
Choose: 2
# Creates: track_1.mid, track_2.mid, ..., track_10.mid
# Use in: DAW for individual editing/mixing

Practical Multitrack Tips

Start with rhythm: Record drums/percussion on Track 1 first
Layer bass next: Track 2 provides harmonic foundation
Add harmonies: Tracks 3-6 for chords and melodies
Use Track 10 for leads: Easy to clear/re-record solos
Name your tracks (in DAW after export for reference)

🎵 Usage Examples

Recording Your First Track

Power on (default: REC mode, Track 1 selected)
Press Button 2 (Start recording)
- RED LED and Track 1 LED blink
Play your melody on Casio keyboard
Press Button 2 (Stop recording)
- LEDs stop blinking
- Track auto-saves

Layering Additional Tracks

Press Button 4 (Right) to select Track 2
Press Button 2 (Start recording)
- Track 1 loops in background as you record Track 2
Play complementary part
Press Button 2 (Stop)

Playing Back All Tracks

Press Button 1 to switch to PLAY mode
- YELLOW LED lights up
- All recorded tracks' LEDs light up
Press Button 2 (Start playback)
- All tracks play together, looping continuously
Press Button 3 (Pause) to pause/resume
Press Button 2 (Stop) when done

Exporting Your Composition

SSH into Pi: ssh pi@raspberrypi.local
Type: save
Choose: 1 (merged) or 2 (separate tracks)

Transfer file to Mac:

scp pi@raspberrypi.local:~/looper_exports/merged_output.mid ~/Desktop/

Loading Existing MIDI

Transfer MIDI file to Pi:

scp bass_line.mid pi@raspberrypi.local:~/

SSH into Pi and load it:
```
load 3 ~/bass_line.mid
```
Track 3 now contains that MIDI data

🔧 Technical Details

MIDI Recording

Captures all MIDI messages: note on/off, velocity, sustain, mod wheel, etc.
Records timing with microsecond precision
No quantization - records exactly what you play

Looping Mechanism

Tracks loop based on longest track duration
Example: Track 1 (5s) + Track 2 (10s) → Track 1 loops twice per cycle
Seamless loop transitions

Memory Usage

Each MIDI event: ~50 bytes
1GB RAM can store ~20 million events
Practical limit: hours of recording before RAM fills

Tone Independence

Records MIDI data only, not audio
Your keyboard interprets the MIDI
Change sound on Casio anytime - recording adapts
Example: Record in Grand Piano, play back as Strings

🔌 Power Requirements

Pi + LEDs: ~500mA @ 5V (2.5W)
Recommended: 5V 2.5A+ power supply
Compatible: Phone chargers (22.5W+), official Pi adapter, quality power banks

⚠️ Check for under-voltage:

vcgencmd get_throttled
# Output should be: throttled=0x0

🐛 Troubleshooting

Casio Not Detected

# Check connected MIDI devices:
python3 -c "import mido; print(mido.get_input_names())"

# Replug USB cable, wait 10 seconds, try again

LEDs Not Working

Check GPIO connections match pinout
Verify GND connections
Test individual LED: gpio -g mode 20 out; gpio -g write 20 1

Under-Voltage Warning

Use better power supply (5V 2.5A minimum)
Avoid long/thin USB cables
Don't use USB hub power

Service Won't Start

# Check logs:
sudo journalctl -u looper.service -n 50

# Stop service for manual testing:
sudo systemctl stop looper.service
python3 looper.py

Session Not Auto-Loading

# Check autosave file exists:
ls -lh ~/looper_autosave/session.json

# If corrupted, delete and start fresh:
rm ~/looper_autosave/session.json

🚦 LED Behavior Reference

LED	Steady On	Blinking	Flashing
RED (Rec)	Recording mode active	Currently recording	-
YELLOW (Play)	Playing mode active	-	-
BLUE (Pause)	Playback paused	-	-
WHITE (Clear)	-	-	Track cleared
RED (Delete)	-	-	All tracks deleted
Green (Track)	Track selected OR has data	Recording on this track	-

⚠️ Important Notes

Recording is overwrite mode - Re-recording a track erases previous version
Touch sensor deletes everything - Use carefully!
No resistors = LED risk - PWM helps, but don't run 24/7
Auto-save is automatic - Manual save only for MIDI export
Backing tracks loop during recording - Hear context while recording new parts

📝 Future Enhancements

🤝 Contributing

Feel free to submit issues, fork the repository, and create pull requests for any improvements.

📄 License

MIT License - Feel free to use and modify for your projects!

🙏 Acknowledgments

Built with:

mido - MIDI library for Python
RPi.GPIO - Raspberry Pi GPIO control
Casio CTX870IN keyboard

📧 Contact

For questions or suggestions, open an issue on GitHub!

Happy Looping! 🎹🎵

Name		Name	Last commit message	Last commit date
.DS_Store		.DS_Store
Looper.py		Looper.py
README.md		README.md

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🎹 Raspberry Pi MIDI Looper

✨ Features

🛠️ Hardware Requirements

Components

Optional

📐 Pin Connections (BCM Numbering)

Buttons (Pull-Up, connect to GND)

Touch Sensor (Active High)

Status LEDs (Anode to GPIO, Cathode to GND)

Track LEDs (Green, Anode to GPIO, Cathode to GND)

Ground Distribution

🎛️ Button Functions

Button 1: Mode Toggle (GPIO 5)

Button 2: Start/Stop (GPIO 6)

When Stopped in REC Mode:

When Stopped in PLAY Mode:

When Running:

Button 3: Left/Pause (GPIO 13)

When Stopped in REC Mode:

When Playing in PLAY Mode:

Button 4: Right/Clear (GPIO 19)

When Stopped in REC Mode:

When Playing in PLAY Mode:

Touch Sensor: Delete All (GPIO 26)

💾 Software Features

Auto-Save System

CLI Commands

MIDI Export

MIDI Import

Track Status

🚀 Installation

1. Flash Raspberry Pi OS

2. Install Dependencies

3. Upload Looper Script

4. Test Manually

5. Enable Auto-Start (Optional)

📁 File Transfer (Mac ↔ Pi)

From Mac to Pi

From Pi to Mac

Using SFTP (Alternative)

🔒 Super Looper Mode

Key Features

Activating Super Looper Mode

Using Super Looper Mode

Recording Behavior

Deactivating Super Looper Mode

Session Management

Checking Status

When to Use Super Looper

🎼 Multitrack Usage Guide

Understanding Track Channels

Recording Multiple Tracks with Different Tones

Backing Track Recording

Looping Behavior

Tone Independence

Track Management

MIDI Export Options

Practical Multitrack Tips

🎵 Usage Examples

Recording Your First Track

Layering Additional Tracks

Playing Back All Tracks

Exporting Your Composition

Loading Existing MIDI

🔧 Technical Details

MIDI Recording

Looping Mechanism

Memory Usage

Tone Independence

🔌 Power Requirements

🐛 Troubleshooting

Casio Not Detected

LEDs Not Working

Under-Voltage Warning

Service Won't Start

Session Not Auto-Loading