Many many years ago there were strong men whose job was to raise the bellows for organ wind,
finally arrived some invisible men...
take a look at the video:
Organ Graziadio Antegnati (1565) - Mantova- ITALY
restored by Giorgio Carli
Umberto Forni plays:
Ricercare super "My Favorite Things"
(prima pars - alio modo - chromatica - passacagli ad libitum)