BioComputer Music : Generating Musical Responses with Physarum polycephalum -based Memristors Edward Braund and Eduardo Miranda Interdisciplinary Centre for Computer Music Research (ICCMR) Plymouth University, UK edward.braund@students.plymouth.ac.uk eduardo.miranda@plymouth.ac.uk Abstract. This paper introduces BioComputer Music, an experimental one-piano duet between pianist and plasmodial slime mould Physarum polycephalum. This piece harnesses a system we have been developing, which we call BioComputer. BioComputer consists of an analogue cir- cuit that encompasses components grown from the biological computing substrate Physarum polycephalum. Our system listens to the pianist and uses the memristive characteristics of Physarum polycephalum to pro- duce a list of notes to generate a musical response with, which it plays through electromagnets placed on the strings of the piano. Such electro- magnets set the strings into vibration, producing a distinctive timbre. Physarum polycephalum is an amorphous unicellular organism that has been discovered to exhibit memristive qualities. The memristor changes its resistance according to the amount of charge that has previously flown through. In this paper we introduce the general concepts, technology and musical composition behind the BioComputer Music piece. Our rationale for using Physarum polycephalum is also discussed. Keywords: Physarum polycephalum, Memristors, Unconventional Com- puting for Music, Computer Music, Biomusic, Biological Engineering 1 Introduction The field of computer music has evolved in tandem with advances made in com- puter science. We are interested in how the field of unconventional computation [4] may provide new pathways for music and related technologies. In computer music, there is a tradition of experimenting with emerging technologies. Until re- cent years, developments put forward by the field of unconventional computation have been left unexploited, which is likely due to the field’s heavy theoretical nature, complexity and lack of accessible prototypes. Uniquely, the biological computing substrate Physarum polycephalum requires comparatively fewer re- sources than most other unconventional computing substrates: the organism is cheap, openly obtainable, considered safe to use and has a robustness that al- lows for ease of application. It is for these reasons we have selected Physarum