Well, there is this sample code for generating a DSP beep on the player...

#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <math.h>

#define EMPEG_DSP_MAGIC 'a'
#define EMPEG_DSP_BEEP _IOW(EMPEG_DSP_MAGIC, 0, int)

int main(int ac, char *av[])
{
int fd;
int pitch = 60;
int duration = 500;
int args[2];

fd = open("/dev/dsp", O_RDONLY);

if (ac == 3)
{
pitch = atoi(av[1]);
duration = atoi(av[2]);
}

if (fd < 0)
{
perror("Couldn't open dsp.\n");
return 1;
}

args[0] = pitch;
args[1] = duration;

if (ioctl(fd, EMPEG_DSP_BEEP, args) < 0)
perror("ioctl.\n");

usleep(duration * 1000 + 125000);

close(fd);

return 0;
}

I notice you can pass pitch and duration args to it...all you'd really need is an interface.