XMF is a family of music-related file formats created and administered by the MIDI Manufacturer's Association. XMF is based on the idea of containing one or more files in existing formats – such as Standard MIDI Files, DLS instrument files, WAV or other digital audio files, etc. – to create a collection of all the resources needed to present a musical piece, an interactive webpage soundtrack, or any other piece of media using pre-produced sound elements.

There are two parts to XMF: the XMF Meta-File Format, which all XMF files use, and a series of XMF File Types that use the XMF Meta-File Format for various purposes. So far, XMF Type 0 and XMF Type 1 files have been defined.

XMF Meta-File Format – XMF is designed to keep file sizes as small as possible, in order to be useful on systems ranging from small-footprint mobile devices like cell phones to desktop/laptop computers to high-power web servers. It also has no maximum file size, so it could be used to store very large collections if desired. To support international music data commerce, the meta-data that travels with the resources can be International, keyed to the user's language and the country in which playback is happening – so in an XMF album, the liner notes could change language depending on who's listening.

XMF File Types – XMF Type 0 and XMF Type 1 files are Standard MIDI Files that can use both standard General MIDI instruments provided by a player, and custom DLS instruments. The MIDI files and the DLS files are bound together in the XMF file, rather than travelling separately where they can get lost. (This approach, which allows for reliable, rich-sounding music at very reasonable file sizes, was pioneered by Beatnik, Inc., who led the MMA working group that developed the XMF design.) Type 0 and Type 1 are identical, except that in Type 0 the MIDI data may be streamed.

The MMA expects to approve additional XMF File Types in the future, for different purposes, as MMA member companies identify the need for them.

No. Although XMF and XML are both extensible, XMF avoids XML technology in order to minimize overhead, data size, and code size.

Just get the XMF Specification documents and start implementing.

No. XMF is freely usable. The only thing you have to pay for is buying the specification documents.

No, but you will probably need to obtain the specification documents from the MMA.

Not from the MMA at the moment. But we may make something available in the future.

XMF is a technology for wrapping collections of other music and sound resource types, such as MIDI files and DLS and digital audio files. XMF itself does not describe musical notes, notation, instrument sounds, or audio recordings. Instead, it gives content creators a way to pull all those elements together into a single file, for easier handling and more consistent, predictable playback.

The XMF container format allows a collection to include files on remote web servers, via URL, just as easily as including data directly in the XMF file. Flexible data compression is also built directly into the container, for faster file downloads.

There are several different types of XMF file, and the answer to this question depends on which type you mean.

The most popular use of XMF is currently for mobile phone content, via the Mobile XMF file type. Many mobile phones can already open and play Mobile XMF files; check your phone's documentation. See our XMF Products page for a partial list of Mobile XMF file authoring tools. 

XMF music/sound player software for other music composition applications should also appear shortly. If developers will let us know about them, we'll post the information on our XMF Products page.

You can arrange the resources in an XMF file in any hierarchy you prefer, like the folders and files in a file system. You can add custom resource types to an XMF file very easily, and any other application that opens the file will ignore them. You can also add custom Meta-Data items to any resource, and control whether other applications will be able to read and display it. You can apply your own data-compression or encryption system at the individual resource level (although other applications will not be able to read those packed resources). Extensions that prove generally useful can be incorporated into the public XMF standard at any point, if you wish.

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