For audio I/O there are at least three possibilities,
from what is
probably easiest to hardest:
PortAudio
Jack
ALSA
Don't forget RtAudio:
http://www.music.mcgill.ca/~gary/rtaudio/
Particularly in combination with STK's RtWvOut object, using it is
nice and simple:
------------
#include "RtWvOut.h"
#include <math.h>
int main()
{
RtWvOut dac;
int i=1;
while (i++)
dac.tick(sin(i*6.28*440/44100));
}
------------
Steve