# python3 and ffmpeg can both be installed easily via the Synology Package Manager

# ensure python3 installed
python3 --version 

# ensure pip3 installed
sudo python3 -m ensurepip

# install scdl
python3 -m pip install scdl

# test install (note that binary not added to path, I did not bother with this)
/var/packages/py3k/target/usr/local/bin/scdl --version

# test script
sudo /var/packages/py3k/target/usr/local/bin/scdl -l https://soundcloud.com/naaaateeee -f --download-archive archive.txt --sync archive.txt -c -n 50 

# or, run without waiting for the result!
sudo /var/packages/py3k/target/usr/local/bin/scdl -l https://soundcloud.com/naaaateeee -f --download-archive archive.txt --sync archive.txt -c -n 50  > output.log 2>&1 &
# outputs a PID, cancel with kill -9 PID