Piano

Notes

Sonic Pi plays all piano keys. The command play 70 means the 70th key, play 71 plays the next to the right. Sonic Pi plays also decimal notes, try play 71.67. Also, you can play multiple notes at the time:

play 72
play 75
play 79

Melody

Use sleep command in between.

play 72
sleep 0.5
play 75
sleep 0.5
play 79