MIDI (Musical Instrument Digital Interface) is a popular protocol for communicating musical information between electronic devices. It allows you to create and manipulate musical data such as notes, durations, and velocities. If you’re interested in incorporating MIDI sequencing and playback functionality into your C++ project, you’re in the right place! In this blog post, we’ll explore how to achieve MIDI sequencing and playback using C++.

Setting Up the Environment

Before we dive into the code, we need to set up our development environment. We’ll be using the RtMidi library, which provides a simple and cross-platform API for MIDI input/output. Make sure you have the following prerequisites:

1. C++ compiler (such as GCC or Clang)
2. RtMidi library (install via package manager or from source)

Once you have the necessary tools installed, we can start coding!

MIDI Sequencing

To get started with MIDI sequencing, we need to create a MIDI file and add some musical data to it. Here’s an example of how to create a simple sequence of notes:

#include <iostream>
#include "RtMidi.h"

int main() {
    RtMidiOut midiOut;
    midiOut.openVirtualPort("MIDI Sequencer");

    // Create a MIDI message for each note
    std::vector<unsigned char> message;

    // Set the instrument to piano (channel 0)
    message.push_back(0xC0);
    message.push_back(0x00);
    midiOut.sendMessage(&message);

    // Play a C4 note for 1 second
    message.clear();
    message.push_back(0x90);
    message.push_back(60); // C4
    message.push_back(100); // Velocity
    midiOut.sendMessage(&message);
    std::this_thread::sleep_for(std::chrono::seconds(1));

    // Stop the note
    message.clear();
    message.push_back(0x80);
    message.push_back(60); // C4
    message.push_back(0); // Velocity
    midiOut.sendMessage(&message);

    // Close the MIDI output port
    midiOut.closePort();

    return 0;
}

In this example, we use the RtMidi library to open a virtual MIDI output port and send MIDI messages to it. We set the instrument to piano and play a C4 note with a velocity of 100 for 1 second. Finally, we stop the note and close the MIDI output port.

MIDI Playback

To play back a MIDI file using C++, we can utilize the RtMidi library in combination with a MIDI file parser, such as the midifile library. Here’s an example of how to play a MIDI file:

#include <iostream>
#include "RtMidi.h"
#include "midifile\include\MidiFile.h"

int main() {
    RtMidiOut midiOut;
    midiOut.openVirtualPort("MIDI Player");

    smf::MidiFile midiFile;
    midiFile.read("example.mid");

    // Iterate over each event in the MIDI file
    for (int eventIndex = 0; eventIndex < midiFile[0].getSize(); eventIndex++) {
        smf::MidiEvent event = midiFile[0][eventIndex];

        if (event.isNoteOn()) {
            std::vector<unsigned char> message;
            message.push_back(0x90); // Note On
            message.push_back(event.getKeyNumber());
            message.push_back(event.getVelocity());

            midiOut.sendMessage(&message);
        } else if (event.isNoteOff()) {
            std::vector<unsigned char> message;
            message.push_back(0x80); // Note Off
            message.push_back(event.getKeyNumber());
            message.push_back(0); // Velocity

            midiOut.sendMessage(&message);
        }

        std::this_thread::sleep_for(std::chrono::milliseconds(event.tick * 10));
    }

    // Close the MIDI output port
    midiOut.closePort();

    return 0;
}

In this example, we use the RtMidi library to open a virtual MIDI output port and the midifile library to read a MIDI file called “example.mid”. We iterate over each event in the MIDI file and send the corresponding MIDI messages to the output port. We also introduce a delay between events based on the tick value to maintain the correct timing.

Conclusion

In this blog post, we explored how to implement MIDI sequencing and playback functionality using C++. We used the RtMidi library for MIDI input/output and the midifile library for parsing MIDI files. By leveraging these tools, you can easily incorporate MIDI capabilities into your C++ projects. So why not start creating your own music sequencers or MIDI players today?

#programming #cpp #MIDI #sequencing #playback