EUHARMONIC ORGAN, is a very improved musical instrument, the first that has ever been capable of producing perfect harmony, or music wherein none of the harmonies are tempered or imperfect, in the widest range of modulation, the inveniton of the Rev. Henry Liston, minister of Ecclesmachan in Scotland, for which he tool out a patent in 1810 ; (see the Phil. Mag. vol. xxxcii. p. 328, vol. xxxix. p.421 ; and the Monthly Mag. vol. xxxvi. p.217). The first of these instruments was perfected in Edinburgh, and had a separate pipe for each of the numerous sounds wanted. The 12 finger-keys in common use were made to act always on as many contiguous notes of the scale, by means of six pedals, discharging to sharps at a time, and bringing on as many flats, or vice versa, in the order of modulation ; single pedals, or foot movements being a most important improvement on the separate hand-slides in the harpsichords constructed on Dr. Smith's plan, and in the organ of the Foundling Hospital, London ; and it is somewhat remarkable, that the same system and construction of pedals occurred about the same time to Mr. David Loeschman in London, who afterwards took out a patent for applying the same to his improved organs and piano-fortes, for tempered systems. Besides the # and b pedals above described, Mr. Liston had others for occasionally shifting the finger-key movements from one pipe to another, higher or lower than it, by the interval of a major comma.

In order to lessen the bulk and expence of this first construction of his organ, Mr. Liston afterwards contrived a mode of temporarily lowereing the sound of a pipe, either by one or two commas, and restoring it again at pleasure, by means of a shader, brought and held near to it, but not touching its orifice ; and for this contrivance for diminishing the number of pipes, and for some improvements in the bellows, was Mr. Liston's patent obtained. After exhibiting this improved organ during a session in London, to the most eminent of the musical professors and amateurs, Mr. Liston published his Essay on Perfect Intonation, a handsomely printed quarto work of 144 pages, besides 40 quarto pages of closely printed music, separately done up, to accompany it. This important work, forming a new era in the theory of music, and its practice on keyed instruments, is prefaced by the most handsome and voluntary testimonials of four eminent London professors, who had performed on and heard the euharmonic organ. The first part of this work treats of the perfect scale, temperament, and the principles and construction of the euharmonic organ ; the second part treats of musical chords, and their progressions, modulations, intervals, and their combinations in chords, modulation within the key, and passing into subordinate keys, &c. ; and, lastly, notes illustrative of the text. The engraved examples contain full and very explicit instructions for learning the use of the euharmonic organ, in every key and kind of modulation, and euharmonic changes ; and the selection of pieces of music, from many of the best masters, which follow, being all, like the elemetary examples that precede them, exactly marked wherever the different pedals are to be pressed by the foot or released, during performance, in order to produce the exact perfect chords that the several composers intended ; and such, indeed, as the amateurs of music are daily in the habits of hearing, in the performances of correct singers, either alon, or accompanied only by separate perfect instruments for single parts, like the violin, violincello, sliding trumpet, &c. (whereon the exact pitch of the notes can be instantly varied at pleasure), or performances wholly by such perfect instruments, for a band of good performers ; whose refined and delightful harmony had never, in any considerable degree, been produced, by a single performer, before the exhibition of the patent organ of which we are speaking.

The euharmonic organ seems an essential requisite instrument to the singing master, by which, in the shortest and most perfect manner, a habit of correct intonation in the various keys, and harmonizing with their fellow performers in every case, might be acquired, and fixed in his pupils ; and not only so, but practising often with such an instrument would give almost equal precision to the performance of those discords that occur, and so essentially contribute to the beauties of most compositions, whien correctly given, as they are on this organ, but which, it is presumed by the writer, very rarely happens even with our best performers of single parts in concert, for want of any audible phenomenon, like the beats of imperfect concords, to exactly fix the point of perfection in a discord, while learning to perform, or in practising, as the cessation of beats do for the concords ; and, accordingly, he was most forcibly struck on first hearing Mr. Liston's organ, with the perfectly new and peculiar character of several of the discords, when heard alone, but more especially when combined in certain chords ; the pleasing effect ,for instance, of the II\, 7/, IX (and 7/), and what is more surprising, of the #VI, (and #II and IV), when combined, as Mr. Liston describes in pages 57, 69, 73 and 99 of his Essay, and wherein he mentions also at page 56 (and 99) and 71 ; the disagreeable effect of 7 (and 5, II and IV) in the dominant seventh, and of 2 in the chord of the greater seventh, &c.

To teachers and students of the violin, violincello, &c., the euharmonic organ would prove a valuable guide and test for stopping in tune, particularly with the discords. And, above all, to the theoretic musician and composer this instrument cannot fail of proving at all times useful, for trying the precise effect of every combination of harmony that may suggest itself, and for beneficially extending the bounds of this difficult part of the science. (g)