There is a world of difference between practising a piece of music and performing that piece of music. When practising you have in mind an ideal that you strive, in your own time, to realise, but when performing you give immediate expression to that ideal in real time. For the duration of the performance the ideal effectively vanishes and is replaced by spirit: the spirit of the composer, the spirit of the performer and the spirit of the event. Only a critic would be mean-spirited enough to refuse the numinous and make comparisons.