K3YS3NS3 (KeySense) is the products and services side of basicmusictheory.com, owned by Instacosa S.L.U., a company registered in Spain.
In the future, expect to see more premium quality physical products (like the Key Cards) for sale in the U.S. and Europe.
Also, on the way, a range of reference E-Books for learning music.
Hope you find them useful!
To get email reminders when new things appear in your region, head over to the basicmusictheory.com signup page
The Key Cards will be first launched in U.S. in Q4 2018, then in UK and Europe in 2019.