The harpsichord is an instrument larger than a spinet, with two or three strings to a note.
This text comes from a footnote on a diary entry in the 1893 edition edited by Henry B. Wheatley.
daniel • Link
Harspicon was simply a charming seventeenth century variant spelling of the harpsicord, a keyboard where strings were plucked with plectra.
Chart showing the number of references in each month of the diary’s entries.