Что не так с переменной?

from tkinter import *
from tkinter.ttk import Combobox, Checkbutton
 
drums = ["False", "False", "False", "False", "False", "False", "False", "False"]
currentDrum = 0
global cmb
global ckb
 
window = Tk()
 
chk_state = BooleanVar()  
chk_state.set(False)
 
def cbSelected(event):
    currentDrum = int(cmb.current())
    if drums[currentDrum] == "False":
        chk_state.set(False)
    else:
        chk_state.set(True)
    
 
def cbCheck():
    print(currentDrum)
    if chk_state.get():
        drums[currentDrum] = "True"
    else:
        drums[currentDrum] = "False"
    
window.title("Title")
window.resizable(False,False)
window.geometry("400x176")
 
gp = LabelFrame(window, text="Sort", width=401, height=56)
gp.place(x=0,y=0)
 
cmb = Combobox(gp, width=54, height=22)
cmb.bind("<<ComboboxSelected>>", cbSelected)
cmb.place(x=5,y=5)
cmb['values'] = ('Sort "kick" samples', 'Sort "clap" samples', 'Sort "snare" samples', 'Sort "hi-hat" samples', 'Sort "hat" samples', 'Sort "ride" samples',  'Sort "crash" samples', 'Sort "tom" samples')
cmb.set('Sort "kick" samples')
 
ckb = Checkbutton(gp, width=1,var=chk_state, takefocus = 0, command=cbCheck)
ckb.place(x=366,y=5)
 
gp2 = LabelFrame(window, text="Samples folder", width=401, height=56)
gp2.place(x=0,y=55)
 
txt = Entry(gp2, width=59)
txt.place(x=5,y=5)
 
bt = Button(gp2, text="...", width=3)
bt.place(x=365, y=2)
 
bt2 = Button(window, text="Start sort", width=20, height=1)
bt2.place(x=125, y=120)
 
statusbar = Label(window, text="Ready", bd=1, relief=SUNKEN, anchor=W)
statusbar.pack(side=BOTTOM, fill=X)
 
menu = Menu(window)  
file_item = Menu(menu,tearoff=0)  
file_item.add_command(label='Exit') 
menu.add_cascade(label='File', menu=file_item)
 
help_item = Menu(menu,tearoff=0)
help_item.add_command(label='About')
menu.add_cascade(label='Help', menu=help_item)
window.config(menu=menu) 
 
window.mainloop()

global currentDrum