In the eleventh century, when musical notation came into being, a monochord was used to teach singing. The clavichord followed in due course, and by a rapid process of development regals, organs, and virginals evolved. The virginal, although distinct, was associated with the spinet, which with the later harpsichord may be found in houses which have been but little disturbed since the middle of the eighteenth century. It was in that century that the piano came, but not until it was well advanced, for in an old playbill of Covent Garden Theatre, published in 1767, it was announced that "Miss Brickler will sing a favourite song from _Judith_, accompanied by Mr. Dibdin on a new instrument called the piano forte." Of such instruments and of earlier types there are many fine examples in the Victoria and Albert Museum at South Kensington, in the Royal Scottish Museum, and in the Crosby-Brown Collection in the Metropolitan Museum of Art in New York City. In Fig. 89 is seen a beautiful spinet in excellent condition. Whistles and Pipes. It is said by the exponents of artistic furnishing and decoration that no home can be complete without music, for it gives an atmosphere of art which nothing else can impart; and certainly a collection of household curios cannot be complete without some musical instrument, although but a humble example. It may be a moot point among collectors whether the insignificant whistle or primitive call can be regarded as sufficiently musical to rank in this category. It is certain, however, that it is one of the commonest of sound producers; if there is a boy in the home there is almost sure to be a whistle in the house. Few trouble about the scientific explanation of the sound produced by this common instrument, but experts tell us that the sound comes because condensations occur by the collision of air against the cutting edge placed in its path. Of antique whistles there are many types, those shown in Fig. 90 being the most frequently met with. The one marked "D" is said to be an attempt to increase the volume of sound by the extension of a cutting edge. A double sound is produced by that marked "F," whereas "A" is of the more familiar type, the example illustrated being an ivory whistle used upwards of a hundred years ago. From the whistle came the tin pipe capable of producing tunes in the hands of a skilful player. The whistle and pipe were in olden times associated with coaching days and inns. At one time it was customary for a whistle to be attached to the handles of spoons used on inn tables. Thirsty travellers blew the whistle when refreshment was required, and from that custom we get the common expression, "You may whistle for it." The horn, too, was a favourite instrument, and very necessary in days gone by, when it served many useful purposes.