I had this problem in sibelius 6. Slurs are not sounding correctly in strings and the timpani roll doesn't sound right, it plays too perfectly. Both these things worked until sibelius released an update. I went on their forum earlier this year and are aware of the problem. There are many things that people suggested, from changing dictionary settings to changing the soundset to make it "sound" like its legato. Why should i have to do this. I got gpo4 because of its ability to integrate with sibelius so that when sibelius tells gpo4 there is a slur I at least get a legato sound. I have recently upgraded to sibelius 7 to find these problems haven't been solved which leads me to believe the problem lies with gpo4. If anyone else has had similar problems or has any advice on how to fix it, it would be greatly appreciated.