Audsley and Wedgwood describe this stop as a 16' pedal Tibia Plena (an open flute). Bonavia-Hunt describes it as a large-scale bass Clarabella with leathered lips. Irwin claims that it is usually a Tibia Clausa of 16' pitch in the manuals, or 32' pitch in the pedal, and occasionally an open rank of large scale. Williams specifies 16' or 32' pitch.

Tibia Profundissima

Tibia Profunda 32', 16', Pedal; Hammond Castle, Gloucester, Massachusetts, USA.

Tibia Profunda 16' (wood), Great; Tibia Profunda 32', Pedal (ext. of Great); Town Hall, Melbourne, Australia; Hill, Norman & Beard 1929.

Tibia Profunda 16' (wood & iron), Pedal; Tibia Profunda 16' (metal), Great; Worcester Cathedral, Worcester, England; Hope-Jones 1896.

Tibia Profunda 16', Recitativo, Pedal; Basilica S. Pietro, Vatican, Italy; Tamburini 1954.