Wobbly Garageband audio from outdoor keyboard recording

I recorded my friend playing on an electric keyboard in an outdoor area, but when I listened back to the playback in my house, I realised the piano audio sounded a bit strange:

I recorded this on my scarlett solo 3rd gen. Connected the mono output of the keyboard to the interface with a 1/4" cable, also had a condenser mic running with phantom power on at the same time. I haven't had a problem with recording mic and another instrument simultaneously before. Would appreciate any help!

[Edited by Moderator]