LM556 is a dual timer that can be operated as two LM555.
The two timers operate independently of each other sharing only VCC and ground.You can define timing by provide an external resistor and capacitor for each timer.
This circuit is a 3-state sound generator.The IC is defined to generate audio frequency one for high audio frequency and one for low audio frequency .
You can use this tool to obtain the values of R and C for your desire sound.
When S1 was selected for each position the sound will generated by
1. Two tone
2. Steady tone
3. Tone burst