Question: who is the current lead singer of the band chicago
[{'answer': 'Robert Lamm', 'provenance': [{'wikipedia_id': '168876', 'title': 'Chicago (band)', 'start_paragraph_id': 2, 'start_character': 460, 'end_paragraph_id': 2, 'end_character': 471, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]