Apps for the Organ Music

I am interested in developing an apps that will detect the pitch of the singer and play the correct notes for the song according [ Harmonium, Piano, etc.] for given Raga. If the raga is selected for a song, this apps should automatically pick up the pitch of the person singing and will play tune according to the ups and downs of the Raga. The apps should pick up the Pitch 'C' and play the correct notes in the same Raga [ie: if the raga is Shankaraparanam and the person's pitch is '"C"' - The apps should pick up the Pitch 'C' and play the correct notes in tha Raga (Shankaraparanam).] Like that, It should pick up the pitches and play for many different Ragas.