Hi Dave,
don’t think so, it’s not one of the apps mentioned the sx Yamaha site, think it only works with an assortment of pianos.

I plugged it in , just to try it, but no luck.

I will be replacing my lightning adapter because I’m pretty sure it’s faulty, it drops in and out.

I’ll give it another try when I get my new one, but I don’t think the app will work with the sx900.

Some of the others sound interesting though, chord tracker . No idea what it does yet.