Born in Chicago and raised in New Rochelle, New York, Janet Maguire began musical studies at the age of six: on piano, French horn, and cornet.

She completed a BA degree in Piano at Colorado College, then went to Paris to study composition with René Leibowitz for five years.

They co-authored the book Thinking for Orchestra: Practical Exercises in Orchestration (published by G. Schirmer), and a book about the orchestration of some of Jacques Offenbach's works, Nuits Parisiennes (RCA, Bote & Bock), as well as Carl Maria von Weber's opera Die Drei Pintos.

Several summers spent at the Darmstadt Ferienkurse influenced Maguire's style, as did the music of György Ligeti, Luigi Nono, and Karlheinz Stockhausen.

Her compositions have been heard throughout Italy and Germany, and in France, Spain, Ireland, the UK, the US, Austria, Canada, Argentina, Australia, Latvia and Bulgaria.