This paper presents a new guitar dataset made out of richly annotated guitarist improvisations. The annotations include notes, playing techniques, instrument tuning, audio effects configurations as well as transcriptions of post improvisation interviews. The dataset gathers ten hours of improvisations and around five hours of interviews. These accompanying data make this dataset suitable for a variety of research domains : from MIR to musical improvisation analysis and musicology. The recordings that have yielded to this dataset were done in the context of an hexaphonic multieffect practice study. This hexaphonic multieffect is meant to work with an hexaphonic guitar (one pickup per string guitar) and grants the player with independent audio effects configurations for each string. This paper presents the dataset, and the experiment it has been gathered from. It also details, based on the transcriptions of the interviews, a first analysis of the specificities of an hexaphonic multieffect practice.