Linux MIDI: a Brief History, Part 1
The OSS/Free kernel sound API supported the basic MIDI capabilities of the original SoundBlaster soundcards. This offered a maximum of 16 channels--no support for multiport interfaces--and support for hardware interfaces only in UART mode, also called dumb mode for its relatively simple capabilities. The OSS/Free API supported a raw MIDI device, /dev/midi, and an advanced device, /dev/sequencer, for interfaces controlling the timing of the MIDI data queue.
From kernel 2.6 onward, ALSA (the Advanced Linux Sound Architecture) is the kernel sound system. Among its many features, ALSA includes backwards-compatibility with OSS/Free MIDI support while offering new support for more modern MIDI systems, including a sequencer architecture that allows easy connections between ALSA sequencer clients and a module for creating virtual MIDI ports on machines without MIDI hardware--very handy on my laptop. ALSA's MIDI hardware support includes standalone MIDI cards, soundcard MIDI hardware connectors, serial and parallel port interfaces and USB MIDI interfaces. The system also installs some useful MIDI utilities, such as the aconnect sequencer client router, the amidi tool for sending and receiving raw MIDI data and the amidirecord utility for recording a standard MIDI file at the command prompt. Besides the OSS/Free /dev/midi and /dev/sequencer devices, ALSA adds its own /dev/snd/midiCxDx logical devices, where C is the card number and D is the device number.
The ALSA sequencer API is a most welcome evolution in Linux MIDI support. Compliant programs may be connected freely, with multiple inputs allowable on a single port. Graphic patch bays are available that display and edit the send/receive status of the available clients. Incidentally, ALSA's virmidi (virtual MIDI) ports appear to the system as though they are real ports, and their data may be routed to and from any other port, real or virtual.
I also must mention that Linux MIDI support extends to a number of operating system and CPU emulation environments, with especially good results achievable with DOSemu, an MS-DOS emulator, and XSteem, an AtariST emulator.
At the least, a complete software-based MIDI music-making environment should include a MIDI sequencer, a rhythm programmer and one or more software synthesizers. Serious MIDI musicians also should include helper applications, such as patch bays and MIDI event filters. Many interesting MIDI composition environments are available, including MIDI programming languages and GUI-based programs. Music notation programs especially have benefited from MIDI connectivity. Standard MIDI files are fairly easy to convert to notation, and your notated compositions can be rendered and performed easily by way of MIDI.
In Part 2, I will describe Linux programs and utilities in all of these categories. For now I leave you with some eye candy taken from the current Linux MIDI software scene. Enjoy!
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