One source of error is found in the evolution which musical instruments have undergone. In the time of Bach and Haendel the bow truly merited its Italian name of "arco." It was curved like an arc--the hairs of the bow constituted the chord of the arc, a very great flexibility resulting which allowed the strings of the instrument to be enveloped and to be played simultaneously. The bow seldom quitted the strings, doing so only in rare cases and when especially indicated. On this account it happens that the indication of "legato" is very rare. Even though there was a separate stroke of the bow for each note, the notes were not separated one from the other. Nowadays the form of the bow is completely changed. The execution of the music is based upon the detached bow, and although it is easy to keep the bow upon the strings just as they did at the commencement of the nineteenth century, performers have lost the habit of it. The result is that they give to ancient music a character of perpetually jumping, which completely destroys its nature. The very opposite movement has been produced in instruments of the key or piano type. The precise indications of Mozart show that "non-legato," which doesn't mean at all "staccato," was the ordinary way of playing the instrument, and that the veritable "legato" was played only where the author specially indicated it. The clavecin or harpsichord, which preceded the piano, when complete with two banks of keys, many registers giving the octaves and different tone qualities, oftentimes like the organ with a key for pedals, offered resources which the piano does not possess. A Polish lady, Madame Landowska, has studied thoroughly these resources, and has shown us how pieces written for this instrument thus disclosed elements of variety which are totally missing when the same are played upon the piano; but the clavecin tone lacked fulness, and shadings or nuances were out of the question. Sonority or tone was varied by changing the keys or register just as on the organ. On the other hand, with the piano one can vary the sonority by augmenting or diminishing the force of the attack, hence its original name of "forte piano,"--a name too long, which was shortened at first by suppressing the last syllables; so that one reads, not without astonishment, in the accounts given of young Mozart, of the skill he showed in playing "forte" at a time when he was playing on instruments of a very feeble tone. Nowadays when athletic artists exert all their force upon the modern instruments of terrific sonority, they are said to play the "piano" (_toucher du piano_).