Question: which of the righteous brothers sang unchained melody
[{'answer': 'Bobby Hatfield', 'provenance': [{'wikipedia_id': '359664', 'title': 'Unchained Melody', 'start_paragraph_id': 3, 'start_character': 97, 'end_paragraph_id': 3, 'end_character': 111, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]