As far as gameplay is concerned,
Guitar Hero: On Tour is nearly identical to the console versions. The game is broken up into single-player Career and Quick Play modes as well as a two-player Duel mode. The version on display was missing a number of songs, though the selection was rather expansive and included songs like "China Grove" (The Doobie Brothers), "All the Small Things" (Blink 182) and "Rock and Roll All Night" (KISS). The final version will, of course, include a larger number of songs (around 25) and include tracks exclusive to the DS version as well as a few favorites from
Guitar Hero III. The final list will include songs like "Spiderwebs" (No Doubt), "Jessie's Girl" (Rick Springfield), "This Love" (Maroon 5) and "What I Want" (Daughtry).
As far as the sound quality is concerned, the game sounds much better than I was expecting. In order to get the best audio experience possible, it is probably best to play with a set of headphones, but when heard it through the DS's speakers, the music was much better than the tracks found in other games (Elite Beat Agents, for example).
Guitar Hero: On Tour also features a robust and incredibly fun two-player mode. The Co-op options allow you to play with a friend, one playing lead and the other playing bass, though the real fun is found in Guitar Duel. Similar to the duel mode featured in Guitar Hero III, On Tour's competitive mode features a number of power-ups meant to really trip up your opponent. These include things like speeding up the notes or increasing the difficulty as well as blown amps (cutting out the music) or a flash bulb that temporarily whites out the screen, making it hard to see the notes.