YouTuber loopop has released a free Lemur template that lets you play melodies on a Novation Circuit. He's even gone through the trouble of creating dedicated templates for both iPhone and iPad screens.
This Lemur template will let you play melodies with samples on the Novation Circuit. You can use the iPhone or iPad screen to play melodies, and if you have an external MIDI keyboard you can hook that up as well.
Besides playing live, you can also record yourself - check out the video for more details. Enjoy!
Here's the iPhone template:
and here's a template for the iPad: