I find this list of systemSoundID very useful for accessing the sound ID directly.
http://iphonedevwiki.net/index.php/AudioServices
For example, to play a key press tock sound.
#define systemSoundID 1104
AudioServicesPlaySystemSound (systemSoundID);
You’ll also need to add the AudioToolbox framework in your project, and add #include <AudioToolbox.h>
to your .m or .h file.