What we have is a hybrid of the old and the new. Frequency and Amplitude were the first steps that Harmonix took into the music-game genre and represent the heritage of Rock Band Unplugged. Rock Band proper is the culmination of Harmonix's efforts over the last seven years and continues to entertain as the new face of the rhythm-action genre. This special brew succeeds on a surprising strength, but may alienate its target audience for the very same reason: the game is ball-crushingly hard.

There are the usual front-end options to create a ‘world tour’ band with four members and, should you feel so inclined, hilarious, ambiguous or just plain stupid names. You also have the option to mess around in Quickplay, Warm-Up or the new Band Survival mode but there are no multiplayer modes or scoreboards. This was obviously designed as a single-player experience, but a bit of online ‘scoreboating’ would have been a welcome addition.

The essential element of the game is lane switching. The action is split into four ‘lanes’ of music presented in the traditional Rock Band style – coloured notes fly towards the bottom of the screen and you press the corresponding button at just the right moment. For stalwarts of the sub-genre, the first oddity is the colour placement of the notes. There are only four notes per track and they run red, yellow, green, blue. This is different from either the guitar or drum charts from its bigger brother and veterans may find this off-putting at first. There seems to be no good reason to alter the colour chart in this way.

Then comes the first kick to the groin. This game is hard. It is initially harder than its console counterpart because of the control scheme. On the d-pad left = red, up = yellow, while triangle = green and circle = blue. The L and R buttons switch lanes and X = Overdrive. Splitting the lane up so half is attributed to each hand on the PSP seems to be ultimately the best control configuration, but it really takes a lot of effort to get used to. Expert Rock Band players are advised to play a tutorial or risk becoming instantly frustrated with this portable rocker.

Once you have pulled your head around the control scheme, the second kick is the amount of control you need to exert over the game to succeed. Players of Frequency and Amplitude will be used to lane switching, new players will not. You are required to tend to four lanes of notes at the same time. Bass sits on the left, then drums, followed by vocals and guitar on the right. Once you have hit 100% of a section of notes in one lane it will disappear (the sections can vary in length from one note to tens of notes) and you then switch to the next lane using L or R. The scoring system has a heavy bias towards chaining the lanes so you instantly move to the next available lane (this is simplified thanks to several visual clues pointing you in the right direction) and then hitting all 100% of the notes in that section. Repeat that process until you get to the end of the song. So, to do well you need to be far more accurate than Rock Band. If you fail to 100% a section you lose your chain and the section remains uncompleted for you to try again.

Kick three is the ‘New Super Mario Bros.’ of kicks. If you ignore a track for too long or consistently fail to 100% a section in it – the track blinks red and eventually dies. So you need to stay on top of chaining the lanes together to succeed at all in this game. Overdrive builds up in the usual way: by hitting all the glowing white notes. Doing so will reward you with a quarter of a bar of power. Once you have half a bar or more you can activate Overdrive to double your score multiplier, or save any dead lanes you previously massacred. There is a lot more going on than you may first imagine, and therein lies the defining characteristic of Rock Band Unplugged.

It's character-building stuff. Imagine jumping naked into a freezing cold lake with the partner of your dreams. The initial shock is so harsh that all you can think of is running away with your tail between your legs in search of a comforting blanket to cry into. Get over the difficulty and persevere with the obstacles presented to you and you’ll find an absolute gem of a game to pleasure your senses with.

It is precisely because so much is going on at once that once everything clicks into place you uncover one of the most absorbing music experiences there is to be enjoyed. Switching deftly between the four lanes, chaining all your beats and maxing out your Overdrive is the most engrossing experience available in the music-action genre. You need to employ maximum concentration (and headphones are definitely required for this) to achieve the Zen-like state needed to enjoy Rock Band Unplugged, but when you get there the feeling you get is so unbelievably connected to the music that you’ll want to repeat it often.

Intertwined with the joy of the trance-inducing gameplay is the rarest of things in a modern game: an actual difficulty curve. As the game is so initially difficult to wrap your head and hands around, there is a real sense of progression and achievement on offer. You know when you are doing well in Rock Band Unplugged because you can feel it, you don’t need the (plentiful) visual tricks to spur you on – your own motivation to succeed is inspiration enough. The more your abilities grow, the greater the sense of accomplishment you get from the simple premise of hitting the right button at the right time. Arguably this attribute is inherited wholesale from the title’s older brother but here, because you control all aspects of each song and you need to be 100% perfect all the time, it just feels like more of an achievement to really nail a track.

Which brings us neatly on to the songs themselves. With 41 tracks (all master recordings) in the game you might think that is enough for a portable title. However, the truth of the matter is not so simple. On the plus side there is a DLC option that allows you to expand the experience, at a price, of course. On the negative side, a large selection of the music on offer is a re-imagining of the tracks from Rock Band 1 and 2. The note charts may be different, and it is a new way to play, but it would have been nice to feature a bit more new music.

Along that same vein, those expecting the excellent musical range of Frequency and Amplitude will be disappointed. The track listing is definitely more mainstream than its grandparents' (where is my techno Bowie remix?) and may disappoint long-term lane switchers with its lack of variety. Hopefully, Harmonix will address this complaint with some more exclusive DLC content, but only time will tell.

Oddly for a Rock Band game, there is a good deal of repetition in the World Tour mode. At the beginning of the tour the same tracks will appear frequently, often disguised as a set list in one city and individual songs in another location. To complete, the World Tour songs will need to be played multiple times. That’s great for high score aficionados, but a poor design choice for casual players.

Realistically, though, it won’t be casual players who get the most from Rock Band Unplugged. It will be the old school, the hardcore and the dedicated. Score chasers and perfectionists will love the challenge offered by the hardest difficulty settings, and the definite sense of achievement it provides. As a portable companion to the Rock Band franchise this really couldn’t be any better. The control system, while initially confusing, becomes well thought out with the addition of hindsight. The game design is tight and, whilst initially bewildering, becomes manageable and enjoyable with practice. The presentation, while for the most part irrelevant to the central experience, is excellent throughout and the sound, with a decent set of headphones, is also of a very high quality.

Buy this game if you want a challenging title that will eat up long journeys or quiet evenings in darkened room; it’s a great take on the franchise and it’s made for us, for the fans.