GayGamer writes: "Portable music games always seem like an odd duck. Guitar Hero On Tour for the Nintendo DS had to create an attachment so you could press down on the usual buttons while "strumming" on the touch screen. But all the PSP has are some buttons and a thumbstick. So how in the world did Harmonix think they were gonna pull off Rock Band Unplugged without any guitars, drums or microphone? Well, it turns out by skewing the gameplay back towards their earlier titles Amplitude and Frequency."