How to use the operator <> of overlay

Hello, I'd like to ask you a question about overlay.

d1 $ sound ( overlay "bd sn:2" "cp*3" )
I hear it's the same as d1 $ sound ("bd sn:2" <> "cp*3")
I'm going to use <> in the tidal cycle, but it is not recognized.
How can overlay operator <> use code?