The base resistor would go in series with the base, but you may need another much higher value base resistor too from the base to ground.
The transistor turns on around 0.7 volts so you need the audio to have at least a 0.7v peak. I dont know what the ipod voltage output is but if it's less than that it wont turn the transistor on.
You could also try a large value base resistor from base to +Vcc as a bias resistor. Then a capacitor could be used to couple in the signal to the base. You'd have to experiment with the resistor value though starting from say 100k and working down to maybe 10k.
The idea is to get the transistor where it almost turns on with the resistor to +Vcc, then when the audio input goes positive it turns the transistor on. This may require a pot. Not sure how reliable this setup would be however, it may need adjustment now and then.