DryWetMIDI is the .NET library to work with MIDI files. Visit Wiki to learn how to use the DryWetMIDI. The library was tested on 130,000 files taken from here. Thanks midi-man for this great collection. You can get the latest version via NuGet.

Features

With the DryWetMIDI you can:

• Read, write and create Standard MIDI Files (SMF). It is also possible to read RMID files where SMF wrapped to RIFF chunk.
• Finely adjust process of reading and writing. It allows, for example, to read corrupted files and repair them, or build MIDI file validators.
• Implement custom meta events and custom chunks that can be written to and read from MIDI files.
• Easily catch specific error when reading or writing MIDI file since all possible errors in a MIDI file are presented as separate exception classes.
• Manage content of a MIDI file either with low-level objects, like event, or high-level ones, like note (read the High-level data managing section of the Wiki).
• Build musical compositions (See Pattern page of the library Wiki).

Getting Started

There are several articles that can help you dive into API provided by DryWetMIDI:

• DryWetMIDI: High-level processing of MIDI files
• DryWetMIDI: Notes Quantization

Let's see some examples of what you can do with DryWetMIDI.

To read a MIDI file you have to use Read static method of the MidiFile:

var midiFile = MidiFile.Read("Some Great Song.mid");

or, in more advanced form (visit Reading settings page on Wiki to learn more about how to adjust process of reading)

var midiFile = MidiFile.Read("Some Great Song.mid",
                             new ReadingSettings
                             {
                                 NoHeaderChunkPolicy = NoHeaderChunkPolicy.Abort,
                                 CustomChunkTypes = new ChunkTypesCollection
                                 {
                                     { typeof(MyCustomChunk), "Cstm" }
                                 }
                             });

To write MIDI data to a file you have to use Write method of the MidiFile:

midiFile.Write("My Great Song.mid");

or, in more advanced form (visit Writing settings page on Wiki to learn more about how to adjust process of writing)

midiFile.Write("My Great Song.mid",
               true,
               MidiFileFormat.SingleTrack,
               new WritingSettings
               {
                   CompressionPolicy = CompressionPolicy.Default
               });

Of course you can create a MIDI file from scratch by creating an instance of the MidiFile and writing it:

var midiFile = new MidiFile(
                   new TrackChunk(
                       new SetTempoEvent(500000)),
                   new TrackChunk(
                       new TextEvent("It's just single note track..."),
                       new NoteOnEvent((SevenBitNumber)60, (SevenBitNumber)45),
                       new NoteOffEvent((SevenBitNumber)60, (SevenBitNumber)0)
                       {
                           DeltaTime = 400
                       }));
midiFile.Write("My Future Great Song.mid");

or

var midiFile = new MidiFile();
TempoMap tempoMap = midiFile.GetTempoMap();

var trackChunk = new TrackChunk();
using (var notesManager = trackChunk.ManageNotes())
{
    NotesCollection notes = notesManager.Notes;
    notes.Add(new Note(NoteName.A,
                       4,
                       LengthConverter.ConvertFrom(new MetricTimeSpan(hours: 0,
                                                                      minutes: 0,
                                                                      seconds: 10),
                                                   0,
                                                   tempoMap)));
}

midiFile.Chunks.Add(trackChunk);
midiFile.Write("My Future Great Song.mid");

If you want to speed up playing back a MIDI file by two times you can do it with this code:

foreach (var trackChunk in midiFile.Chunks.OfType<TrackChunk>())
{
    foreach (var setTempoEvent in trackChunk.Events.OfType<SetTempoEvent>())
    {
        setTempoEvent.MicrosecondsPerBeat /= 2;
    }
}

Of course this code is simplified. In practice a MIDI file may not contain SetTempo event which means it has the default one (500,000 microseconds per beat).

To get duration of a MIDI file as TimeSpan use this code:

TempoMap tempoMap = midiFile.GetTempoMap();
TimeSpan midiFileDuration = midiFile.GetTimedEvents()
                                    .LastOrDefault(e => e.Event is NoteOffEvent)
                                    ?.TimeAs<MetricTimeSpan>(tempoMap) ?? new MetricTimeSpan();

Suppose you want to remove all C# notes from a MIDI file. It can be done with this code:

foreach (var trackChunk in midiFile.GetTrackChunks())
{
    using (var notesManager = trackChunk.ManageNotes())
    {
        notesManager.Notes.RemoveAll(n => n.NoteName == NoteName.CSharp);
    }
}

or

midiFile.RemoveNotes(n => n.NoteName == NoteName.CSharp);

To get all chords of a MIDI file at 20 seconds from the start of the file write this:

TempoMap tempoMap = midiFile.GetTempoMap();
IEnumerable<Chord> chordsAt20seconds = midiFile.GetChords()
                                               .AtTime(new MetricTimeSpan(0, 0, 20),
                                                       tempoMap,
                                                       LengthedObjectPart.Entire);

To create a MIDI file with single note which length will be equal to length of two triplet eighth notes you can use this code:

var midiFile = new MidiFile();
var tempoMap = midiFile.GetTempoMap();

var trackChunk = new TrackChunk();
using (var notesManager = trackChunk.ManageNotes())
{
    var length = LengthConverter.ConvertFrom(2 * MusicalTimeSpan.Eighth.Triplet(),
                                             0,
                                             tempoMap);
    var note = new Note(NoteName.A, 4, length);
    notesManager.Notes.Add(note);
}

midiFile.Chunks.Add(trackChunk);
midiFile.Write("Single note great song.mid");

You can even build a musical composition:

Pattern pattern = new PatternBuilder()
     
    // Insert a pause of 5 seconds
    .StepForward(new MetricTimeSpan(0, 0, 5))

    // Insert an eighth C# note of the 4th octave
    .Note(OctaveDefinition.Get(4).CSharp, MusicalTimeSpan.Eighth)

    // Set default note length to triplet eighth and default octave to 5
    .SetNoteLength(MusicalTimeSpan.Eighth.Triplet())
    .SetOctave(5)

    // Now we can add triplet eighth notes of the 5th octave in a simple way
    .Note(NoteName.A)
    .Note(NoteName.B)
    .Note(NoteName.GSharp)

    // Get pattern
    .Build();

MidiFile midiFile = pattern.ToFile(TempoMap.Default);