4. The later medieval use of organs, from about 1450 onwards, is implied in wills which are primarily bequests to employ singers, very often chantry-priests. One, two or even three organs became quite common in town churches and in richer country areas, newly-fashionable rood-lofts being sometimes equipped with a small ‘portatyf’ (that is, easily portable, but not hand-held) used during special liturgies. The organ used every day was often placed on the north side of chancels alongside the singers’ seats ; towards the end of the fifteenth century their sound were made more flexible dynamically by an earlier redeployment of the key sliders as rank-sliders, to stop off some individual ranks of pipes. The invention of these ‘stops’ may have been due to English or Flemish makers ; finger keyboards and key pallets were presumably developed from the key actions of the strap-carried tiny processional organ.
Organ players were usually first trained as boy singers ; in both singing and playing they improvised descants and basses to the plainsong melody. Playing alternated with singing, verse by verse, and – copying the vocal style they had learnt – organ players developed an ornamented keyboard style. The title of ‘organist’ was not official in many cases until the 19th century, and this peculiarity underlines the historically close association of the English organ with its own ‘vocal’ sonorities with voices in churches. In secular music, organs were played in consort with other instruments such as viols and sackbuts in dances, ‘fancies’ and in solo song.
It is possible that by the early 16th century there were around 4,000 organs in Britain, some very large ; research to try to refine this figure is going on at present. See my web-site : soundsmedieval.org for further information.