Add first song from Lesson 9
user
```ruby
# Lesson 9 - More Chords: D, E, A and B Flat
# Rhythm - Left Note/Right Chord (Hit the Road, Jack)
use_synth :piano

play :D3
sleep 0.5
play chord(:D4, :minor)
sleep 0.5

play :C3
sleep 0.5
play chord(:C4)
sleep 0.5

play :Bb2
sleep 0.5
play chord(:Bb3)
sleep 0.25

play :A2
sleep 0.75
play chord(:A3)
```
assistant