ID3V1

public ID3V1Tag ID3V1 { get; set; }

using (Metadata metadata = new Metadata(Constants.MP3WithID3V1))
{
    var root = metadata.GetRootPackage<MP3RootPackage>();

    if (root.ID3V1 == null)
    {
        root.ID3V1 = new ID3V1Tag();
    }

    root.ID3V1.Album = "test album";
    root.ID3V1.Artist = "test artist";
    root.ID3V1.Title = "test title";
    root.ID3V1.Comment = "test comment";
    root.ID3V1.Year = "2019";

    // ...

    metadata.Save(Constants.OutputMp3);
}