Auditory chimaeras are synthesized by combining the envelope of one sound with the fine structure of another. This study investigates the perceptual importance of these two features in speech reception, pitch perception, and sound localization. The envelope is crucial for speech recognition, while the fine structure is important for pitch and sound localization. When these features conflict, speech is localized by the fine structure, but words are identified by the envelope. This finding supports the hypothesis of separate 'what' and 'where' pathways in the auditory cortex. Speech–noise and speech–speech chimaeras were tested, revealing that speech reception depends on the number of frequency bands. With more bands, speech reception improved when information was in the envelope but deteriorated when in the fine structure. Speech–speech chimaeras showed that envelope information dominated, while melody–melody chimaeras showed the opposite, with fine structure dominating at higher band numbers. Sound localization in dichotic chimaeras was based on the fine structure's ITD, consistent with previous findings. The study suggests that cochlear implants could benefit from incorporating fine-structure information to improve pitch perception and ITD sensitivity. The Hilbert transform was used to extract envelope and fine structure, providing a mathematically rigorous method. The results indicate that envelope information is more perceptually important than fine structure, especially in speech. The findings have implications for improving auditory processing in cochlear implants and understanding auditory pathways.Auditory chimaeras are synthesized by combining the envelope of one sound with the fine structure of another. This study investigates the perceptual importance of these two features in speech reception, pitch perception, and sound localization. The envelope is crucial for speech recognition, while the fine structure is important for pitch and sound localization. When these features conflict, speech is localized by the fine structure, but words are identified by the envelope. This finding supports the hypothesis of separate 'what' and 'where' pathways in the auditory cortex. Speech–noise and speech–speech chimaeras were tested, revealing that speech reception depends on the number of frequency bands. With more bands, speech reception improved when information was in the envelope but deteriorated when in the fine structure. Speech–speech chimaeras showed that envelope information dominated, while melody–melody chimaeras showed the opposite, with fine structure dominating at higher band numbers. Sound localization in dichotic chimaeras was based on the fine structure's ITD, consistent with previous findings. The study suggests that cochlear implants could benefit from incorporating fine-structure information to improve pitch perception and ITD sensitivity. The Hilbert transform was used to extract envelope and fine structure, providing a mathematically rigorous method. The results indicate that envelope information is more perceptually important than fine structure, especially in speech. The findings have implications for improving auditory processing in cochlear implants and understanding auditory pathways.