Revisiting the known and unknown misprints in Purcell's 'Dioclesian'

Despite its seemingly authoritative primary source, the music in Henry Purcell's opera Dioclesian, printed in movable type by John Heptinstall in 1691, poses numerous textual problems. Based on a study of four copies of the score in the British Library, the article highlights a pattern of misprints which seems to have been idiosyncratic to Heptinstall's workshop, and suggests that the working method of one of the workshop's compositors, whereby he miscalculated the position of the notes on the stave, resulted in wrong readings and 'mirror related' notes - notes whose type seems to have been erroneously inverted. The mechanism of 'mirror related' readings is analysed and collated with other features of house style in order to retrieve information regarding the printing process and the printers involved. The article also discusses performers' possible responses when encountering such doubtful readings, and the significance of such responses to present-day editorial work.