1. The analysis by Stockhausen himself that provides a detailed explanation of the work and how to orient for its realization. Both the re-composition of the instrumental score and the choice of parameters for the electronic part are explained by the composer. In this explanation we can find the main rules to prepare the different versions, how to choose the parts of the score, the criteria for the timbre solutions and finally the different organisation schemes of the live electronic performance then conceived using the magnetic tape. From the initial version of the score explained by the composer we arrive today to the different versions of the live electronics realised with digital technologies. The electronics part is based primarily on the effects of delay and feedback. Already in the '90s it was possible to replace the magnetic tape with digital technologies. One of the first examples of a digital realisation is described in my article Software for the definition of instruments in electroacoustic music: Mikrophonie I and Solo (Bologna, 1986).
2. Currently there are many interesting solutions for the realization of the effects in recent applications that allow the performer to execute and monitor the entire performance. We will show the iPhone application realised by A. Petrolati and E. Francioni. The evolution of Solo toward a soundscape, a version with voice and instruments performed outside in a seascape location, derived from this application