If your car doesn't have Bluetooth or an auxiliary input, you can still play music from your iPhone using a cassette adapter or FM transmitter. A cassette adapter works by inserting the cassette into your car's cassette player and plugging it into your iPhone's headphone jack. An FM transmitter broadcasts music from your iPhone to your car's FM radio. You can also consider upgrading your car's audio system to one that is compatible with Bluetooth or auxiliary input.