LECT. XVIII. REED INSTRUMENTS. 341 



until its length is double that of the column of air, which 

 would give the same sound as the reed. At this point the 

 pitch again rises to the fundamental note of the latter. 



Let us now devote our attention to the sounds of mem- 

 branous reeds, and especially of those which, by their 

 shape, have great analogy with the glottis, and which con- 

 sist of a lamina of caoutchouc, having an opening in their 

 middle, and which are fixed at the edges of a tube, into % 

 which the air is propelled. It is with apparatus of this sort 

 that attempts have been made to construct an artificial 

 larynx. Let us confine ourselves to the determination of 

 the differences which exist between membranous and me- 

 tallic reeds. Membranous reeds produce sounds which 

 may be greatly modified, by varying their tension. By 

 compressing the membrane, the sound becomes more acute. 

 The principal difference in these two cases consists in this, 

 that membranous reeds produce sounds which are more 

 acute, in proportion as the force of the blast in the tube is 

 greater ; whilst the reverse holds good with metallic reeds. 

 Muller has endeavoured to determine what influence is ex- 

 erted by the porte-vent and body of the tube adjusted on the 

 membranous reed. But we must acknowledge, as does 

 the author himself, that this subject has not hitherto been 

 satisfactorily elucidated. The modifications produced in 

 the sounds of the reeds, by the adjustment of a tube or 

 porte-vent, are considerable. Experiments prove that, ac- 

 cording to the lengths given to them, the sound is at one time 

 raised, at another lowered. I shall relate to you one of the 

 numerous experiments of Muller : with a tube of 6 inches 

 in length, the fundamental sound was re 4 ; this became 

 mi-diese 4, when a tube of 4 inches was added below the 

 tongue ; and with a tube of 4J- inches it rose to re-diese 4 ; 

 with a tube of 8J inches it fell to ut-diese 4, and rose again 

 to re 4 with a tube of 27J inches. 



