You're loud. GuitarFreaks is made by Bemani, same as DDR, and Guitar Hero, for better or worse, completely ripped it off. That said, there are some differences between the two.
1 GuitarFreaks(GF) controllers have 3 buttons max, if I recall correctly. Tilting the guitar acts as a fourth input.
2 Instead of animated, performance-dependent concerts, the GF system is like other Bemani products, a music video playing to the side of the target grid-thing.
3 Because there's no star power, there is a more clearly defined, and more humanly possible, perfect score for each song.
4 To make this more the case, you get different ratings for hitting notes more or less on time.
5 Songs have, of course, multiple sets of targets according to a set of difficulties.
GF has slightly harder challenges, which seems strange until you've remembered that it was around much longer, and the timing ratings mean that the ultimate goal is to hit every note within around 1/64th of a second, not just full combo.