Apple has started to air two new TV advertisements for the iPhone 4S. Like prior commercials for the 4S, the new spots, entitled “Rock God” and “Road Trip”, spotlight the device’s Siri voice-activated virtual assistant. The former shows a teen using Siri to find a guitar, songs to learn, keep a list of possible band names, and schedule band meetings, all before asking the phone to call him by the titular nickname. In…