# AUScheduleParameterBlock A block to schedule parameter changes. ``` typealias AUScheduleParameterBlock = (AUEventSampleTime, AUAudioFrameCount, AUParameterAddress, AUValue) -> Void ``` ## Discussion Check the parameter’s flags to determine whether the parameter is rampable. If a parameter isn’t rampable, a ramp duration of `0` changes it immediately to the target value, and a nonzero ramp duration leaves it unchanged. The block takes the following parameters: - eventSampleTime: The sample time at which the parameter begins changing. When you schedule parameters during the render cycle, such as from a render observer you add with [`token(byAddingRenderObserver:)`](/documentation/AudioToolbox/AUAudioUnit/token(byAddingRenderObserver:)), pass the `AUEventSampleTimeImmediate` value plus an optional buffer offset of fewer than 4096 sample frames to schedule the event at that position in the current render cycle. - rampDurationSampleFrames: The number of sample frames over which the parameter’s return value is to ramp, or `0` if the parameter change should take effect immediately. - parameterAddress: The parameter’s address. - value: The parameter’s new value if the ramp duration is `0`; otherwise, the value at the end of the scheduled ramp. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)