The Concert at the Varieties.—The Varieties Theatre was opened last evening for the concert announced to he given by Professor Van HiitHeu and Madaine Neville Mercier-Bier, and long before the curtain rose, the auditorium was lilled with professional musicians and dilittanti of the city, all of whom were manifestly anxious to enjoy the treat that had been prepared for them.The occasion was particularly marked by the 'fact that Madame Bier was to exhibit i the progress she had made since her first ap- 1 pearance on the stage, and as well, by the idebut of Miss Kate Thayer, the daughter of our well know n fellow-citizen, Frederick N. Thayer, Esq.An excellent programme had been pre-...... DTpared in which Messrs. Van HutHen, Uel-croix, Gadilhe, Cartier and Madierde Mont-jau participated, but as all these gentlemen are professionally known already we will devote the limited space at our command to the two ladies in whose favor the concert seems to have been specially given. To licgiu, Mine. Bier, we must admit, evinced such remarkable progress since we first heard her at Grunewald Hall, that from the start we began to fear that she had undergone tno severe training, or that she hail devoted herself too assiduously to her art.It became immediately apparent that her voice had undergone a change from a well defined mezzo soprano to a falcon, with an j 1 excellent improvement in the homogeneity i in her registers, for although the writer did , A not express it at the time lie discovered that , V the voice was not “ equal,” or, otherwise, H that the middle register did not harmonize J with the upper and lower ones as it does ■ now.Whether the changes we have noticed are ascrihahle to overwork or to natural causes, we are not prepared to say, and it is | J a matter to 1m* left to her professor, Mr. Van 11 iillleu, to decide.But, as it was demonstrated last evening, while laboring under such a change, a voice should not he subjected to the Polnunise of “ Jerusalem,” the eavatina of “ Ernaui ’• and the grand duo of the third act of the “ Huguenots.” That Mine. Bier sang admirably, and with that intelligence and intensity of expression and finding which destines her to great performances, everybody agrees; hut it would he regretahle at this stage of her “ vocal transition ” to make her sing at the same time contralto and falcon songs of the most difficult in the repertoire.We wish to encourage this young and most promising artist, w ho has no sup rior in this city, hut we must also warn her against disaster that must ensue should she not guard herself against the shoals of musical impracticabilities, attempted only by ccomplished singers, aud we may add, with questionable success.Miss Kate Thayer had a veritable task before her, a lirst appearance and Venzauo’s Italian waltz, on the air da billet de loterie to sing.Her voice is what is called in French that of a chantense legere, ar.d possesses the re-quisite richness, purity,volume aud remarkable flexibility ; besides, as Gueymard said himself to the writer, il y a de la nature, which, coming from this accomplished musician and singer, is more than an ordinary compliment. There is what is know’ll in stage parlance, snap, orjn French, mordant, a more elegant word.Notwithstanding that Miss Thayer’s singing was marred by stage fright, wo can I Mildly assert that she is no amateur, hut is also an artist, whose jiowers of vocalization surprised many who expected to hear only a novice. But of these ladiso we will speak more fully in the future when favorable opportunities present themselves. New Orleans should he proud of both.(A