MIDI Files: DOS to Mac and Back





M I C H I G A N - S C H O O L - B A N D - & - O R C H E S T R A - A S S O C I A T I O N

Barton Polot is Assistant Professor of Music Education and Music Technology at the University of Michigan		BARTON POLOT oday's MIDI technology represents a level of compatibility that has no peer in the world of computers. Virtually all MIDI software supports every make and model of MIDI hardware. Importantly, the files created by any MIDI application can be shared and swapped among all MIDI software for all computers. The lingua franca of computer music is the Standard MIDI File (SMF), a set of conventions adopted by the music industry in 1987 as a superset of the MIDI Standard. SMF is a file format supported by practically all MIDI software developers. Notation software, sequencers, and other music applications allow the user to save music to disk as a SMF as an alternative to the program's native file format. Additionally, most music software will open a SMF, regardless of the software that was originally used to create it. The format is quite robust: track names, patch changes, and subtle nuances are translated without error. Thanks to SMFs, music can be marketed to all computer musicians regardless of hardware. Thanks to SMFs, musicians can create music in one program (say, Band-in-a-Box) and further manipulate it in another (say, Finale). This article explains the one remaining challenge in SMF portability: translating a MIDI file from one computer operating system to another. Moving a file from the Macintosh Operating System (Mac OS) to the DOS/Windows environment (DOS), the Atari ST, or a Bridgeboard-equipped Amiga (both also DOS format) and vice versa takes a few extra steps, but works unerringly. DOS to Mac OS. Using your PC music software, start by saving your file in SMF format on a 3.5-inch disk. Then follow these two steps on your Macintosh.
Figure 1 Apple File Exchange is included with System 6 and System 7 disks. Requires FDHD drive (Macintosh SE and later).		Step one: launch Apple File Exchange, then insert your DOS disk. You will see a window displaying the contents of Mac hard drive on the left, and the contents of your DOS disk on the right (Fig. 1). Select the DOS file you wish to convert, then press the <<Translate button. A Mac OS version of the file will be made on the Mac's hard drive. If desired, you may repeat this process for additional SMFs. When you are finished converting the files, quit Apple File Exchange. Your DOS disk will be ejected automatically upon quitting. You now have a Macintosh version of your SMF, but it is in a generic file format. In order for MIDI software to recognize your file, the file format will have to be changed.
Figure 2 Info dialog box from ResEdit version 2.1. ResEdit is available online, or from your Apple dealer. DiskTools and DiskTop are two popular utilities that also enable you to change the file type.		Step two requires you to launch any Mac application that permits you to change the file format. I recommend ResEdit, although with my standard caveat: the power of ResEdit is awesome. Misuse it, and you can cause irreparable harm to your hard drive. Carefully, then, launch ResEdit; then, in the Open File dialog box, select and open your Mac OS SMF. In the File menu, select "Get Info for your filename." A window appears with many cryptic options (Fig. 2). Your task is to change the file's Type. Delete the text in the box labeled Type, and enter the following four-letter code: Midi (note the upper and lower case letters . . . it must be typed precisely). Quit ResEdit and, when prompted, save your changes to this file. You now have a SMF that can be opened using any Macintosh MIDI software.
		Mac OS to PC. Using your Macintosh music software, start by saving your file in SMF format on your hard drive. Then simply use Apple File Exchange to transfer your file to a DOS-formatted 3.5-inch disk. This strips away the Mac's 128-byte header so that DOS devices can import the file. My students commonly transfer files between systems. With practice, the process becomes routine. Update: since the appearance of srticle in February 1995, Apple's release of System 7.5 has made the use of Apple File Exchange obsolete.