Semi said it was just the one word 'Hell!', so a one shot would be all he needs.
I don't know about whatever arranger he is using, but in most Roland's, as part of the SFX drumkit, there is a 'beep' from an old analog machine that works great...
His might have an equivalent, and I suppose that, if it is on a multipad, you'd need to use a drum kit to stop the arranger from transposing it depending on the chord...
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An arranger is just a tool. What matters is what you build with it..!