MADAME CARADORI ALLAN.--A new star in _our_ musical world has shone upon us during the past month; not the less dazzlingly, perhaps, from its foreign lustre. Mde. ALLAN possesses a _soprano_ voice, of a light quality. She sings with great apparent ease, and there is a finish to every note, worthy of the highest praise. Her execution is graceful in the extreme. The most rapid notes glide as distinctly through her voice as the most slow and measured. There is neither hesitation in the one, nor hurry in the other. All are in exact time, and evince in their execution a degree of study seldom effected, and a taste fully competent to seize upon and display the most exquisite beauties of the art. Her manner is evidently that of one unaccustomed to the stage; that of a sensitive and delicate gentlewoman, suddenly placed in a situation new to her, but embarrassing only from its novelty. If, as has been asserted, Mde. Allan's first appearance here was really her _début_ in an opera made up of English words, she certainly has great reason to congratulate herself on the success which attended even her acting of the part of 'Rosina.' The execution of the opening song, the 'Unâ Voce,' first in English, and then, in obedience to an _encore_, in Italian, was truly as beautiful as we can fancy it in the power of her peculiar voice to make it. It was certainly sufficient to merit one of the most rapturous bursts of applause that was ever listened to. The other music of her part was equally well executed, if we except those pieces where low contralto notes were to be sounded. Here, of course, the artiste could do nothing; and she showed her good sense by attempting nothing. We particularly noticed this peculiarity in the concerted piece at the close of the first act. Having no contralto notes in her voice, it was impossible for her to express the music belonging to this scene. A repetition of 'The Barber,' on the next night, gave us an opportunity of witnessing the same beauties, and the same slight defects. There was, as might have been expected, less embarrassment than on the previous evening; while the acting, and the stage-business altogether, was more easy and natural. 'Love in a Village' displayed the high faculties of Mde. Allan to still greater advantage, and certainly, with one glorious exception, we never heard the melodies which belong to 'Rosetta' more exquisitely given. There were two simple ballads introduced, which, in her way of expressing them, made perfect gems of the hacknied 'Coming through the Rye,' and 'I'm Over Young to Marry.' It is the peculiar province of genius to hallow all it breathes upon; and surely, in a musical way, this truth was never more clearly exemplified. We are sorry to say, however, that with the exception of Mr. PLACIDE, Mde. Allan has been most wretchedly supported. Mr. JONES sang worse than ever, and acted no better. Mr. RICHINGS is not equal to the parts which we honestly believe he is _obliged_ to sustain in opera.