Task: Question Answering
Input (English): Passage: Joy Division toured Continental Europe in January 1980. Although the schedule was demanding, Curtis experienced only two grand mal seizures, both in the final two months of the tour. That March, the band recorded their second album, Closer, with Hannett at London's Britannia Row Studios. That month they released the "Licht und Blindheit" single, with "Atmosphere" as the A-side and "Dead Souls" as the B-side, on the French independent label Sordide Sentimental.A lack of sleep and long hours destabilised Curtis's epilepsy, and his seizures became almost uncontrollable. He often had seizures during performances, which some audience members believed was part of the performance. The seizures left him feeling ashamed and depressed, and the band became increasingly worried about Curtis's condition. On 7 April, Curtis attempted suicide by overdosing on his anti-seizure medication, phenobarbitone. The following evening, Joy Division were scheduled to play a gig at the Derby Hall in Bury. Curtis was too ill to perform, so at Gretton's insistence the band played a combined set with Alan Hempsall of Crispy Ambulance and Simon Topping of A Certain Ratio singing on the first few songs. When Topping came back towards the end of the set, some audience members threw bottles at the stage. Curtis's ill health led to the cancellation of several other gigs that April. Joy Division's final live performance was held at the University of Birmingham's High Hall on 2 May, and included their only performance of "Ceremony", one of the last songs written by Curtis.
Hannett's production has been widely praised. However, as with Unknown Pleasures, both Hook and Sumner were unhappy with the production. Hook said that when he heard the final mix of "Atrocity Exhibition" he was disappointed that the abrasiveness had been toned down. He wrote; "I was like, head in hands, 'Oh fucking hell, it's happening again ... Martin had fucking melted the guitar with his Marshall Time Waster. Made it sound like someone strangling a cat and, to my mind, absolutely killed the song. I was so annoyed with him and went in and gave him a piece of my mind but he just turned round and told me to fuck off.". 
Question: What is the last name of the band members that were unhappy with the man who produced Closer?
Output (English): Sumner.