Instrumental Performance Systems (IPS) help the user to learn how to play a musical instrument, by showing the performance of a song directly on a virtual instrument in the computer screen. Unfortunately, the current IPS exhibit various limitations. For instance, they are hardly editable, or not editable at all, they are not enough interactive and their interface is not fully adequate for string instruments. We are developing D´Accord Guitar, an editable and guitar specific IPS. This paper presents some proposed solutions to unexplored problems found in this development, mainly positioning and fingering. Such problems consist in automatically generating an actual guitar performance based on a sequence of chord ciphers. In order to solve these problems, D´Accord Guitar uses different AI techniques, such as heuristic search, knowledge based approach and constraintsatisfaction solving.