By HECTOR BERLIOZ. Music appears to be the most exacting of all the Arts, the cultivation of which presents the greatest difficulties, for a consummate interpretation of a musical work so as to permit an appreciation of its real value, a clear view of its physiognomy, or discernment of its real meaning and true character, is only achieved in relatively few cases. Of creative artists, the composer is almost the only one who is dependent upon a multitude of intermediate agents between the public a