Busca y reemplaza AppleScript para los nombres de las canciones de iTunes

Estoy tratando de escribir un AppleScript para hacer operaciones de búsqueda y reemplazo masivo de nombres de canciones de iTunes. Actualmente, este es mi código:

tell application "iTunes"
    set sel to selection of front browser window
    if sel is {} then
        try
            display dialog "Nothing is selected…" buttons {"Quit"} with icon 0
        end try
        return
    end if

    set c to (count of sel)

    set theSearchString to display dialog "Find:" default answer "" --prompt for input to search for

    set theReplacementString to display dialog "Replace with:" default answer "" --prompt for input to search for

    repeat with i from 1 to c --set the movement numbers
        set thisTrack to item i of sel
        set songName to (get name of thisTrack)
        set name of thisTrack to (findAndReplaceInText(songName, text returned of theSearchString, text returned of theReplacementString))

    end repeat

end tell

on findAndReplaceInText(theText, theSearchString, theReplacementString)
    set AppleScript's text item delimiters to theSearchString
    set theTextItems to every text item of theText
    set AppleScript's text item delimiters to theReplacementString
    set theText to theTextItems as string
    set AppleScript's text item delimiters to ""
    return theText
end findAndReplaceInText

Actualmente, el findAndReplaceInText() La función devuelve el error 1708. ¿Qué he hecho mal? La función de buscar y reemplazar viene de Apple: Guía de scripts de automatización de Mac - Manipulación de texto