Use standard library style members of wxArrayString (and wxString) ...

... which will make it easier to change the types of those containers to
std::vectors of other string-like classes

for wxString,

IsEmpty => empty
Clear => clear
Alloc => reserve

for wxArrayString,

Count => size
GetCount => size
IsEmpty => empty
Add => push_back
Clear => clear
Empty => clear
Sort => std::sort (only with default comparator)
SetCount => resize
Last => back
Item => operator []
Alloc => reserve

src/FreqWindow.cpp

@@ -239,7 +239,7 @@ FreqWindow::FreqWindow(wxWindow * parent, wxWindowID id,
       /* i18n-hint: This refers to a "window function",
        * such as Hann or Rectangular, used in the
        * Frequency analyze dialog box. */
-      funcChoices.Add(wxString::Format("%s window",  WindowFuncName(i) ) );
+      funcChoices.push_back(wxString::Format("%s window",  WindowFuncName(i) ) );
    }
 
    wxArrayString axisChoices;