I personally think it was a mistake to make viola's the lead instrument, not only for the fact that they sound odd in place of the light tinkly sound originally used, but they're executed a tad too slowly. The sound would do well with more sleigh bells and xylophones for the lead while violins and chellos slowly build up in the background chorus to create a magnificent tangent of music near the climax of the song and slowly die down to the end.