Compressed midi music (eXtended)
XMI is a compressed file format created by XMill. XMI files are XML files, which usually contain metadata information, which have been compressed. XMI stands for “XML Metadata Interchange.” While .XML files tend to be very large, the compression used by XMill into .XMI files will make the files around half the size of other compression techniques. XMI files can be decompressed using XMill or similar XML compression software.
MIME: application/xmill, application/x-xmill
Learn more about .XMI files: