RSE stands for Realistic Sound Engine. Guitar Pro now uses real guitar, bass and drum sounds to play back music. If you're familiar with MIDI and other notation programs, then you know how poorly MIDI guitar sounds. MIDI is a computer generated sound that works well for most instruments but guitar is very difficult to reproduce. Even with expensive sound modules it just doesn't sound realistic. The sound of Guitar Pro is unbelievable. You can choose from a variety of different RSE instruments such as: Electric, Jazz, Classical or Acoustic Guitar, Electric or Acoustic Bass, and even a full drum kit if you want to add a realistic sounding drum track. Guitar Pro lets you choose effects such as delay, reverb, distortion, wah-wah, chorus, flanger and more. This is the only notation program with RSE.