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This paper presents a novel statistical singing voice conversion -LRB- SVC -RRB- technique with direct waveform modification based on the spectrum differential that can convert voice timbre of a source singer into that of a target singer without using a vocoder to generate converted singing voice waveforms .
 used for: direct waveform modification, statistical singing voice conversion -LRB- SVC -RRB- technique; used for: spectrum differential, direct waveform modification; used for: spectrum differential, voice timbre; used for: vocoder, converted singing voice waveforms
Given options, please tell me the relationships of all the listed entity pairs.Output format is "relation1: word1, word2; relation2: word3, word4". 
Option: conjunction, feature of, hyponym of, used for, part of, compare, evaluate for 
Text: {0} 
 Entity Pairs:  direct waveform modification, statistical singing voice conversion -LRB- SVC -RRB- technique; spectrum differential, direct waveform modification; spectrum differential, voice timbre; vocoder, converted singing voice waveforms 
Answer:
 used for: direct waveform modification, statistical singing voice conversion -LRB- SVC -RRB- technique; used for: spectrum differential, direct waveform modification; used for: spectrum differential, voice timbre; used for: vocoder, converted singing voice waveforms