# mutableChannelData(_:) Returns mutable access to a specific channel’s data. ``` func mutableChannelData(_ index: Int) -> AVAudioPCMBuffer.MutableChannelData ``` ## Parameters `index` The zero-based channel index. ## Return Value A `MutableChannelData` enum containing the channel’s sample data. ## Discussion The returned `MutableChannelData` is tied to the lifetime of this buffer and provides type-safe mutable access to the channel’s sample data. - Example: > Warning: This function cannot enforce exclusivity at compile time because `AVAudioPCMBuffer` > is an Objective-C class. The caller must ensure they don’t create overlapping mutable views > to the same memory. It is safe to access different channels simultaneously or different > regions of the same channel. > Note: Provides access to the entire buffer (up to `frameCapacity`). frameLength needs to be updated if the size changes. ```swift for channelIndex in 0..