If you would like to sync data from your NAS to the local disc you might wan´t to mount you NAS or remote volume directly.

install the necessary driver for the remote filesystem and create a mount point:

sudo apt-get install cifs-utils smbclient -y
sudo mkdir -p /mnt/NAS-music
sudo chown -R roon:roon /mnt/NAS-music
# try it out
sudo mount -t cifs //paulus/music /mnt/NAS-music/ -o username=nasuser,password=nasPW

und nun bei Bedarf in die fstab: securely store the credentials:

sudo nano /etc/cifs-credentials

should look like this:

username=your_samba_username 
password=your_samba_password

And now adjust the security 

sudo chmod 600 /etc/cifs-credentials

now edit /etc/fstab and test it

sudo vim /etc/fstab

add

//yourNAS/yourShare /mnt/NAS-music cifs noauto,x-systemd.automount,x-systemd.requires=network-online.target,_netdev,credentials=/etc/cifs-credentials,iocharset=utf8,sec=ntlmssp,ro 0 0

reload and test :

sudo systemctl daemon-reload
sudo systemctl restart remote-fs.target
df -h