The MIDI table.

midi.c

cc -std=c89 -Wall midi.c -o midi

Play note G with velocity of 64.

#include <linux/soundcard.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>

int
error(char* msg, const char* err)
{
  printf("Error %s: %s\n", msg, err);
  return 0;
}

int
main(void)
{
  char* device = "/dev/midi2";
  unsigned char g_on[3] = {0x90, 0x43, 0x40};
  unsigned char g_off[3] = {0x80, 0x43, 0x00};
  int f = open(device, O_WRONLY, 0);
  if(f < 0)
    return error("Unknown", device);
  printf("Note ON\n");
  if(!write(f, g_on, sizeof(g_on)))
    return error("Note", "ON");
  sleep(2);
  printf("Note OFF\n");
  if(!write(f, g_off, sizeof(g_off)))
    return error("Note", "OFF");
  close(f);
  return 0;
}

• PortMidi

incoming hexadecimal