There was soon to be no excuse for not practising in the chill of the winter. This excerpt is from The Musical Times, April 1869:

WARMED PIANOS (G. Price’s Patent) – These Instruments invite playing in Winter, when the coldness of the keys of all others makes it unnecessarily uncomfortable, if not painful, to many, especially children. They encourage practice, and facilitate execution, by a gentle warmth rising from two small hot-water cylinders, of only the diameter of a wine-glass, hidden under their ends, easily handled, and giving a temperature never above “blood heat,” and averaging “summer heat” for three hours. Comfort and perfect suppleness of hands are thus ensured; practice becomes inviting; pupils willing; the master’s time economised; progress uninterrupted; general playing agreeable; and the Piano an article of unmixed pleasure, and most useful, when, in winter, from the absence of outdoor amusements, it is most wanted, but is now most avoided. This improvement is particularly applicable to Harmoniums; the cold air rising from the keys being shut off, and warm air being supplied instead.

A thermometer bulb being inserted in a key shews a maximum warmth below “summer heat”, injurious neither to wood nor glue, whilst the quicksilver of one near the wire and action of Pianos remains stationary. The tone and and mechanism are, therefore, nto affected. These advantages, and a great saving in fires, may be obtained at the cost of a little warm water, and a very trifling outlay.

The warmed Piano – warmth, tone and action guaranteed – may be tested by the trade with thermometers; and, made by the London Pianoforte Company, may be had at the Patentees, 184, Regent-street, from 25 guineas upwards, as well as warmed Harmoniums at the usual prices: Pianos and Harmoniums adjusted with the Warmers, £3 10s; Licenses to “make or alter,” £1 per instrument. An Organ Manual, by Messrs. Hill, Euston-road, may be seen so adjusted. Directions, drawings and particulars, sent at request.

Cited in: Scholes, Percy (1947) The Mirror of Music. London: Novello & Company, vol. 1, p. 301.