How do I use an Arduino to switch another IC's pin (reset) to ground?
The ISD1700 reset pin is active low with an interal 600K pullup resistor, so pulling the pin low with an output pin of the Arduino should work I would guess.

Some things to double check:


Are the ground pins of the Arduino and the Cowlacious audio board connected?
Did you configure the pin on the Arduino to be an output? (pinMode command)


What is the voltage of the reset pin when the Arduino pulls it low? If it is zero, then that part is working. What is the voltage of the pin when the arduino sets it high? If the Cowlicous board and the Arduino have different HIGH voltages then this might cause a problem. In this case you could try leaving the pin as in input except when you pull the pin low. e.g.

pinMode(X, INPUT);
....
digitalWrite(X, LOW);
pinMode(X, OUTPUT);
delay(100);
pinMode(X, INPUT);


or like you say, use a FET to switch it.