Try using an expression like this:
AudioPlaybackOptions(Append(Prompt.Processing, ToAudioBlank(500), Prompt.Processing, ToAudioBlank(500),Prompt.Processing, ToAudioBlank(500),Prompt.Processing, ToAudioBlank(500),Prompt.Processing, ToAudioBlank(500)), true)
The last "true" allows barge-in or not.
The other is to use the ToAudio(MakeList(Prompt.Processing, Prompt.Processing, Prompt.Processing, Prompt.Processing, Prompt.Processing)
Robert