Question: who was the first guitarist to use a wah wah pedal
[{'answer': 'Del Casher', 'provenance': [{'wikipedia_id': '313454', 'title': 'Wah-wah pedal', 'start_paragraph_id': 7, 'start_character': 434, 'end_paragraph_id': 7, 'end_character': 444, 'bleu_score': 1.0, 'section': 'Section::::History.\n'}]}, {'provenance': [{'wikipedia_id': '313454', 'title': 'Wah-wah pedal', 'start_paragraph_id': 7, 'start_character': 0, 'end_paragraph_id': 7, 'end_character': 1705, 'bleu_score': 0.9672634682725431, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12375527271262781395}, 'section': 'Section::::History.\n'}]}]