Imagine this: You have all your music loaded up on your iPhone for a road trip, you jump in your car and then realise you don't have any means of playing it through your car stereo. What can you do if you don’t have a car radio with USB or AUX port?

So what should you do if your old banger doesn't work with your iPhone? We have the answer.

Install CarPlay in your car

Earlier this year Apple launched CarPlay, a iOS connected system that provides direct access to your iPhone allowing you to use certain apps, respond to text messages and play music. Until now CarPlay has only been available as an integrated display system provided as an optional extra when you buy a new car. Various car manufacturers have been integrating this system in their new cars, but we don't all have new cars do we. Read: What is Apple's CarPlay

If you aren't about to buy a new Mercedes then the Pioneer CarPlay system might be a solution for you. We look at the new Pioneer Car Play system that you might be able to add to your own car in the video below.

The 6.2in, 800x480 touchscreen display replaces the existing radio or CD player in your car. It displays information and uses Siri so that your attention is focused on driving. You just say "Hey Siri" to use the assistant hands-free.

There are a limited number of apps available in CarPlay currently, but along with Phone, Messages and Apple Maps you also get Music and Podcasts - so you will be able to play the music on yout iPhone through your car stereo.

Read more about the Pioneer SPH-DA120 in our article about getting CarPlay in your car.

The SPH-DA120 costs £349, but you might also need to budget for converter cables if your car doesn't have standard ISO connectors (most don't) and also a special cable or adaptor if your car has an existing USB port, since it's unlikely to connect directly to the back of the head unit.

What if your car doesn't have the necessary connectors?

It’s hard not to find a modern car radio that doesn’t come with a USB port to connect physically to your iPhone, or, even better for some, a bluetooth connection so you can do the same wirelessly (although this removes the added advantage of being able to charge your phone at the same time, and bluetooth does drain your battery noticeably).

However, what do you do if you don’t have a fancy new stereo in your old venerable car? Are you stuck listening to the radio, CDs, or heaven forbid, cassettes, on your long journeys? Thankfully, no. Some enterprising developers have a handful of easy options for you to connect your high end gadget onto an old car radio and listen to your favourite songs from iTunes without breaking much of a sweat.

Cassette adapters for iPhones

Let’s start with the oldest of the bunch. Some of us undoubtably still use radios equipped with cassettes players. Even though cassettes are no longer manufactured, the hardware is still around, so what can we do with them? Well, it turns out that an ingenious device designed to convert the sound coming from a stereo mini-jack to a modified cassette has been in existence for years. I personally remember using one of those to hook up my portable CD player to a car radio in order to listen to those tracks over fifteen years ago.

Amazingly, you can still purchase them from numerous different companies. A quick look through Amazon for “cassette adapter” will reveal page after page or similar devices ranging in price from £1.99 to upwards of £20. I would imagine a mid-range model would probably be ideal. The way it works is as simple as can be: slot the cassette into the tape deck, connect the mini-jack to your iPhone, choose your song, press play on both the iPhone and your car stereo, and out comes the music. The quality won’t be pristine of course, but it’s much better than the alternative, which would be listening through your tiny iPhone speaker - hardly an immersive experience!

The age of the cassette tape may have passed, but you can still play them in your car via your iPhone

Charging your iPhone in your car

Don’t forget though that playing music will drain your battery so getting yourself a 12V charger for your iPhone would be a useful addition to your car. Again, you’ll find a long list of available options through Amazon, but consider choosing one that can handle enough power to charge up an iPad. Even if you don’t yet own a tablet, more power means your iPhone will charge up faster. Also, should you ever get yourself an iPad, you won’t need another charger for it - you’ll be able to swap between the two devices.

Using your iPhone with your CD player

If your car stereo is more recent and therefore has replaced the tape deck for a CD-player, the above solution will be useless to you, and you can’t put a fake CD connected to a stereo cable in your CD-player: since discs spin, the results would be potentially messy. Which explains why such products don’t actually exist!

iPhone FM transmitters

Instead, you need to look for a clever alternative, one which would also work on those old stereo cassette players: an FM transmitter. These are unsurprisingly more expensive, but they can work very well. The idea is simple: you connect your iPhone (or any other compatible iOS device) to it, and it starts broadcasting your iPhone’s audio on a particular radio frequency. Tune your car radio to that frequency and eh presto, you can hear your music wirelessly.

The Griffin iTrip Auto Universal Plus allows you to connect an iPad or iPhone to your car regardless of the connection type.

It sounds great, but it’s not a flawless solution. There are many radio stations out there so you could hit some interference even if the device usually broadcasts in little used frequencies. You can of course change that frequency manually, but you might end up taking some time finding the perfect one, only to move to another geographical location on your travels and have to do the process all over again.

Which iPhone connector do you have?

Another potential issue is that you need to make sure that device will work for the iPhone you own. And it’s not only the type of connector it has - either the original one or the new Lightning connector, but the innards have changed from generation to generation which means it’s possible that a device that works for the iPhone 3G may not work for the iPhone 4S even though their connector is exactly the same, so a little research will be necessary. Griffin Technology went around this problem with their iTrip Auto Universal Plus, which connects to your iPhone’s stereo minijack, making that device compatible with a wide range of phones and tablets.

Get a ‘Made for iPhone’ car stereo

But to be honest, unless there’s a specific reason why you don’t wish to part with your car’s old stereo, the absolute best option would be to fit a new one. Halfords for instance offer a great many models, all with USB ports and fancy modern features. You need to be careful however: just because it has a USB port doesn’t mean that it will necessarily work with your iPhone; you might be able to hear your music, but your iPhone may not charge, for instance.

It’s therefore important to make sure you get one with a ‘made for iPhone’ sticker. Alternatively, if you can go into a showroom with your iPhone and its cable, the best way to be absolutely sure your potential new car stereo will work as expected is to hook it up to the ones on display and try them out for yourself.

The Philips CE139dr is an in-car stereo that will work directly with your iPhone

Of course, this would be the most expensive solution, but what you’ll get is much better clearer sound (beating the cassette stereos hands down), no interference from radio stations (take that, FM transmitters), plus your phone will be charging while playing, saving you from having to buy a 12v charger. Yes, car stereos can cost upwards of £300, but some iPhone-compatible models will only set you back by as much as £45, and at that price, it may well be worth leaving the past behind and embracing the iPhone-music-enabled future.