Summary

MIDI Visualizer is a live visual effects program for MIDI keyboards. Notes stream upward from the bottom of the screen with color intensity based on key-press velocity — harder strikes produce brighter, more saturated note bars. The project was originally prototyped in Python as a video overlay concept for piano performances, then rebuilt from scratch in Java for performance and threading control.

Architecture

The application runs two parallel threads to decouple time-sensitive MIDI input from rendering:

• MIDI thread: Listens to the system MIDI device via javax.sound.midi, processes NoteOn/NoteOff events, and enqueues note state updates using thread-safe data structures
• GUI thread: Java Swing event dispatch thread reads note state and repaints the canvas at a fixed frame rate, drawing and animating active note bars

Separating these threads eliminated concurrency exceptions that occurred when MIDI callbacks attempted to directly mutate Swing component state.

Features

• Velocity-mapped color: soft touches render cool blue tones, hard strikes render bright white/yellow
• Smooth upward animation with configurable note scroll speed
• Works with any MIDI keyboard connected as a system MIDI device