.\" $OpenBSD: midi.4,v 1.10 2002/03/27 18:10:38 millert Exp $
.\" $NetBSD: midi.4,v 1.4 1998/08/22 14:45:35 augustss Exp $
.\"
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.Dd August 6, 1998
.Dt MIDI 4
.Os
.Sh NAME
.Nm midi
.Nd device-independent MIDI driver layer
.Sh SYNOPSIS
.Cd "midi* at opl?"
.Cd "midi* at pcppi?"
.Cd "midi* at sb?"
.Cd "midi* at wss?"
.Ct "midi* at ym?"
.Ct "midi* at mpu?"
.Cd "pseudo-device sequencer"
.Pp
.Fd #include <sys/types.h>
.Fd #include <sys/midiio.h>
.Sh DESCRIPTION
The
.Nm
driver provides support for various MIDI peripherals.
It provides a uniform programming interface layer above different
underlying MIDI hardware drivers.
The MIDI hardware can be of many different kinds, e.g., an external
synthesizer on a MIDI port (or a serial port), the PC speaker, an
internal FM synth, or a wavetable synth.
.Pp
There are two device file types available for MIDI operation:
.Pa /dev/rmidiN ,
and
.Pa /dev/music .
The
.Pa /dev/rmidiN
devices provides raw access to a MIDI device.
Data written is sent to the physical device as fast as possible and
is uninterpreted. 
Reading from the device returns data as soon as it becomes available.
A moderate amount of buffering is available both for reading and writing.
The raw MIDI devices are mostly useful for non realtime operations, such as
downloading patches to a device, since it is hard to get the accurate timing
needed for quality music from a user program.
But the devices can act as a simple patchboard for MIDI devices.
For example, a MIDI keyboard could be connected to a synthesizer by
the command
.Pp
.Cd "cat -u /dev/rmidi1 >/dev/rmidi2"
.Pp
The
.Pa /dev/music
device is a MIDI sequencer device.
Data sent to and from this device not only contains the information sent to the
MIDI device, but also timing information.
The kernel will make sure that data is sent to the physical device at the
indicated time.
The sequencer device uses the
.Pa /dev/midiN
devices internally and they are unavailable when used by the sequencer.
.Pp
The API for the sequencer device is binary compatible with the OSS sequencer
interface.
.Sh FILES
.Bl -tag -width /dev/sequencer -compact
.It Pa /dev/rmidiN
.It Pa /dev/music
.It Pa /dev/sequencer
.El
.Sh SEE ALSO
.Xr midiplay 1 ,
.Xr ioctl 2 ,
.Xr ossaudio 3 ,
.Xr audio 4 ,
.Xr autri 4 ,
.Xr opl 4 ,
.Xr sb 4 ,
.Xr wss 4
.Sh HISTORY
The
.Nm
driver first appeared in
.Nx 1.4 .