This master thesis has two main objectives, the first is to develop a list of impressionistic key features and the second is to apply those key features when writing idiomatic music for the guitar. The composers of the impressionist era tried to capture the sense of an emotion through the musical language, something this master thesis investigates further. During the process of gathering information about impressionistic key features, I found important building blocks that made me aware of the impressionistic musical language. The four methods I used were arranging and analyzing sheet music, interviews with composers, literature studies and video interpretation. When I found enough material, I started to write music using the impressionistic key features. It resulted in three impressionistic sounding pieces. The pieces are presented with sheet music and an audio recording. As a reader and musician, one can gain knowledge about the impressionistic sound, how to write idiomatic music for the guitar and methods how one can intertwine these two subjects. The discussion part of the thesis addresses problems I struggled with during the process and how I could move away from these difficulties using composing methods and utilizing the impressionistic key features in a creative manor.