splitting a random song

[Unknown_Relic]

this is meant to be a music quiz where they login and need to guess the song by the first letters of each word in the title. When im run the code i get an error with the split_song. Im fairly new to python and i cant find how to fix it.

import random

def access_data():
    with open("Passwords.txt", "r") as f:
        passwords = [line.rstrip("\n") for line in f]
    with open("Usernames.txt", "r") as f:
        usernames = [line.rstrip("\n") for line in f]
    with open("Songnames.txt", "r") as f:
        songnames = [line.strip("\n") for line in f]
    with open("songartists.txt", "r") as f:
        songartists = [line.strip("\n") for line in f]
    return passwords, usernames, songnames, songartists
        
    

def login(usernames, passwords):
    enter_username = input("Input your username")
    if enter_username in usernames:
        enter_password = input("Input your password")
        if enter_password in passwords:
            username_pos = usernames.index(enter_username)
            password_pos = passwords.index(enter_password)
            if username_pos == password_pos:
                print("well done you logged in", enter_username)
                return True
            else:
                print("your password does not match the username")
        else:
            print("password not found")
    else:
        print("username is not authorised")
    return False

def song_selection(songnames, songartists):
    random_song = random.choice(songnames)
    random_songPos = songnames.index(random_song)
    random_artist = songartists[random_songPos]
    print(random_song, "/", random_songPos, "/", random_artist)
    return random_song, random_artist

    
def split_song(songnames):
    print(songnames)
    for letter in songnames.split(" "):
        print(letter[0])

def main():
    passwords, usernames, songnames, songartists = access_data()
    success = login(usernames, passwords)
    if success == True:
        while True:
            random_song, random_artist = song_selection(songnames, songartists)
            split_song(songnames)
            break

main()