Ah, the humble DS Slot 2. Once a praised effort in providing backwards compatibility for those faithfully upgrading from the Game Boy Advance, it succumbed to Nintendo's curse that inflicts an unpleasant flaw with every incarnation of its handheld devices. The GBA required the light of a thousand suns to see anything happening onscreen, the SP lacked the all-important headphone port and the first DS was as ugly as a bulldog licking wee off a nettle. The DS Lite was no different and if you've ever tried to play an Advance cart in this console then you know what I'm talking about; the half-inch protrusion that ruins the clean lines of an otherwise beautiful console and feels so very flimsy and unsafe. Well, now Slot 2 has something to be proud of in the form of the innovative Guitar Hero: On Tour Guitar Grip.

Whilst guitar-based music games aren't new in the gaming world anymore, this is the first edition to hit the handheld market and Red Octane seem to have found a niche with the DS and its highly adaptable touch-screen interface. What we need to determine, however, is whether or not the highly successful Guitar Hero series can cope with being scaled down after we have seen the benefits that DVD and Blu-Ray can provide in terms of sound and video quality, as well as a staggering number of songs (with more regularly becoming available through downloadable content) that can be stored on a hard drive. If these issues are covered with style and grace then the appeal of portable rockin' is easy to see. Why be staring out of the car window, wishing you were somewhere else, when you can be on stage in front of thousands of adoring fans, screaming in delight as you pluck out historic melodies and thrash your way through the ages of rock?

The first thing that everyone will notice is the added hardware bundled in by necessity with the DS cartridge. The game comes with the fancy Guitar Grip, designed to provide the guitar neck button input required to let your chords ring out and your solos melt faces. You can change the look of the whole thing too, through the use of paper inserts that go under the clear plastic shell, a thoughtful addition that's similar to the customisable faceplates of the PS3 Guitar Hero III Les Paul controller. Finally, there is a handy slot in the back where the included pick stylus - a clear, rubber-tipped guitar plectrum - is stored. This connects with a substantial click and feels extremely secure.

Unfortunately, the grip itself does not share this robust sensation when attached to the console's secondary slot. Before I got the hang of holding the DS book-style by the grip, I found it slipping slightly out of the slot, causing the game to throw up an error message and requiring a reboot mid-song; when you're halfway through the solo to Black Magic Woman this can cause screen-busting frustration. Even when I was more comfortable holding the console with just the adjustable hand strap, the unit felt loose and moved slightly in the slot but didn't disconnect. Care is required when playing this game but if you stick to the guidelines in the manual then you should be able to avoid this problem most of the time and, I can gratefully say, save yourself from the agony of the dreaded hand-cramp. When playing PS3 and 360 editions of Guitar Hero, the real guitarist inside of me was ashamed at how quickly I succumbed to the pain, my hand frozen in a disfigured claw until I took a break.

Graphically, the game obviously had to be scaled down but it suits the DS nicely. The screen layout is clean and clear, never becoming too busy. Additionally, when transplanted to a handheld, the decision to use more cartoonish caricatures of rock stars rather than the more realistic visual style of Rock Band proves extremely beneficial. The game is, after all, designed for a handheld console and true immersion isn't the desired effect here. Instead, On Tour provides a similar experience to the early arcade editions where the lure is the thrill of jumping in, rocking out with an entertaining character then wandering off to do something else, distracted by the shiny lights and loud noises of the real world.

The guitars are also fantastically well realised within the game; each axe may be skinned with a range of purchasable paint-jobs and the stylus pick provides a satisfyingly tactile and authentic-feeling interface. Crowds have always been an issue in the Guitar Hero series but, when scaled down, it feels like it really is asking too much to have more than the half dozen individual models repeated throughout the sprawl.

As a niggling issue, some more player-character models would have been appreciated, rather than a rehashing of rockers from the various other instalments of the series. While custom character creation is probably out of the question on the DS, I would have been happier to have found some more varied options when selecting my personal avatar. As it was, I had to settle for the typical grunger (not feeling quite brave enough to squeeze into some leather trousers or sport a three-foot mohawk), always feeling a slight disdain for his mopey attitude and lack of any real variation in his available outfits. When shopping for new gear I wasn't thrilled by the question of what clothes to choose - the red plaid shirt or the green plaid shirt? Oh the possibilities!

By far the most important aspect of a game like this is the quality of the tracks you're jamming along to. With fewer cover versions and some impressive volume (headphones are advised - and polite if you're on the bus!), Guitar Hero: On Tour delivers some knockout tracks from the past forty odd years of rock history. Standout tracks include the speedy Blink 182's All the Small Things and the awesome rock-a-billy Stray Cat Strut by The Stray Cats. There are the usual more obscure songs thrown in as well but they all provide a fun and challenging play through. Crowd noise is also included and, again, while not up to the sing-along thrill of the punters in Rock Band's virtual audience, it provides that extra thrill-burst as you whack everything into Star Mode and hear a roar of appreciation.

On the other hand, if you screw up, a lower score isn't the only form of punishment; hit the wrong note and you are subjected to a painful screech of feedback or a dismaying dead note, which can instantly derail your focus, making it authentically tricky to get back into your groove. In conjunction with this, the crowd also loudly voice their disappointment and displeasure until, especially with headphones on, you find yourself waiting for the first angrily thrown drink to splash against your face.

As a small aside, I'd like to make some comments in defence of the cover versions. They're really not that bad and, yes, while the singer may sound a little off and the band a little too polished, the songs are still perfectly enjoyable and Red Octane have made sure that the copy is as close to the original as possible. Rock stars are busy people too and if the original master is lost then a good cover will always do in a pinch - especially if one or more band members have succumbed to the rock'n'roll lifestyle since the album was released!

So, we've got neat hardware, impressive graphics and awesome sound. That still leaves the question is it fun? Thankfully the answer is yes! On Tour provides an easy to use interface that allows even a Guitar Hero novice to get to grips with the control scheme and play style and be cranking out the tunes in no time. Due to space limitations (especially with my stubby fingers) and issues with holding the unit, there are only four fret buttons on the guitar grip, but Red Octane has compensated for this by finding new and dastardly ways to up the difficulty on the hard and expert levels. Offbeat notes are now more common and varied, while chords can encompass three or four fingers simultaneously, requiring some wickedly fast reactions and brain-straining finger movements. The four-button input device also presents, in my mind, a fine chance for other games to cash in on this new hardware development. I for one am eagerly awaiting the announcement of George Formby's Ukulele Hero with baited breath!

The basics are pretty much the same as if you were holding a real (fake) guitar. You use the buttons on the grip to fret notes and chords (hammer-ons and pull-offs work especially well here) and strum across your guitar's strings on the touch screen. The whammy bar is also included, allowing you to rack up extra points and Star Power by scratching the pick across the screen on long notes.

Star power activation is my only real gripe with the control system. There are a number of options available, the most basic being to tap the Star Meter, launching the blue sparks and doubling your score multiplier until the meter runs out. The other way to do it is to, as suggested by the manual, scream "RAWK OUT!" at the DS microphone. In reality, all that is required is a gentle blow on the mic and, for me, that does the job with minimal fiddling or embarrassment. I learnt my lesson from the Phoenix Wright series that people on public transportation quickly grow tired of the gamer who frequently and seemingly randomly shouts at his DS. The downside of this subtle approach, however, is that the microphone sensitivity is insanely high. Someone sneezing across the room or even the ambient noise inside a car is enough to set off the Star Power, meaning that it is impossible to store enough power for a full meter in such situations.

Given how much Red Octane has crammed into one DS cart in terms of sound quality and visual oomph, the lifespan of On Tour is relatively impressive. The usual Quickplay, Practice and Career modes are present and correct, with twenty-five songs spanning four difficulty levels from Easy to Expert, playable as the lead guitarist or bassist in your very own band (I called mine Plum Krumble). Progression can seem tedious if you aim to get through it in one sitting per level - but that's not really the point of handheld play. Each song lasts no more than five and a half minutes so you can easily whack it on and blast through a few songs before it's time to get off the bus / go to the next lecture / reply to whatever Grandma's talking about. There is also a very complete multiplayer mode with a range of options for co-op play and Wi-Fi battle between DS consoles. If you're familiar with the boss battles from Guitar Hero III then the multiplayer Battle mode will present a welcome addition, with fleshed out mechanics including inventive new attacks such as spontaneous amplifier combustion (requiring you to blow out the flames via the DS microphone) as well as the old arsenal of string breaks and lefty-switch where everything is mirrored for a few moments of bewildering confusion.

Save for a few minor issues, Guitar Hero: On Tour is right on target and suits the handheld format wonderfully. There is invariably a range of problems when introducing new hardware but Red Octane, along with Activision, has succeeded in producing something that, when used correctly, doesn't present too many flaws and is certainly more than adequate. It is, however, disappointing when a solution as simple as some kind of clip for the back of the grip would have been a good idea to prevent slippage. Still, if you're looking for an engaging, entertaining and, most importantly, portable outlet for your inner rock god then look no more because Guitar Hero: On Tour is here.

Reviewed by Henry Osadzinski for AceGamez (All Rights Reserved).