Here's everything we know from playing an early version of this "guitar in a box".
The first thing everyone should get perfectly clear is that Jam Sessions is more of a tool than a game. This isn't a DS version of Guitar Hero…but it might actually make you into a real guitar hero. The idea is really quite simple: strum up and down on the touch screen while holding directions on the D-pad (or face buttons, for lefties) to make different chords. Including diagonals, the D-pad can be programmed to hold eight chords at a time, plus eight more when the shoulder button is held down. Sixteen chords is enough to play almost any popular song from the last fifty years, and that's exactly what Jam Session encourages you to do. The idea is to look up the chord patterns for your favorite songs (or figure them out by ear) and use this DS application as a substitute for a real acoustic guitar.
The main mode is Free Play, in which you can let your imagination run wild to create a new song or play from a chord chart like the ones found at Ultimate Guitar or one of the many songbooks at your local music store. Using the game's extensive options, you can edit the available chords and which directions they are assigned to. There are also eight effects pedals, of which you may use two at any given time. The pedals even have knobs to adjust effects to get just the sound you're looking for. An important part of Free Play is the recording feature, which can store a couple of minutes' worth of guitar strokes for when you're feeling particularly creative. The DS microphone can be turned on if you want to sing to yourself or out through an amplifier, but Jam Sessions cannot record your voice along with the guitar music.
Besides Free Play, there are also around twenty well known songs built into the game. We're not yet allowed to reveal the song titles, but they span multiple generations and genres of music, and even music snobs are guaranteed to find a couple of impressive selections in this list. Jam Sessions doesn't contain the original recordings or even sound-alike covers; it simply shows you the chord charts and lyrics so you can play them yourself. There is a built-in demo for each one (featuring the built-in guitar sounds and a voice synth) that will let you hear the song's rhythm and strumming pattern. However, the total act of playing the guitar part correctly and singing along with the lyrics is complex enough that you probably need to be familiar with the original version in order to produce a decent imitation. At least in our incomplete build of Jam Sessions, there is no edit mode to create chord charts for your own songs or to add in your favorites from online or other sources. Also, we should be clear that even with the built-in songs, you are not playing a traditional music game. The chord chart progresses at your own pace, and there are no penalties for mistakes because there is no score at the end. (In fact, your "mistakes" may have been intentional!)
Jam Sessions is not really a set of guitar lessons – the approach is to teach the basics and then let you learn from experience on songs that you already know. However, there is an interesting set of tutorials called Ear Training. This part of the application is the closest thing to what you would call a "game". It plays a sequence of chords, then asks you to repeat them without seeing their names. The idea is that you will start to recognize certain chords by their sound only, and that will help you learn to play your favorite songs even when you can't find chord charts for them. The patterns you're asked to memorize get pretty complicated, and unlike anything else in Jam Sessions, this mode keeps track of your mistakes and gives a grade at the end of a section. Ear Training could possibly be used to improve your musical recognition.
Jam Sessions is designed to be a very portable (and affordable) acoustic guitar and a way for people who've always had trouble with chord shapes to play the instrument. Stay tuned to NWR for the full song list and an eventual review around the September release date!