I gave up with Chord Tracker app, I couldn't get it to sync via bluetooth with my SX900. 
Hi Allan,
Have you tried connecting Chord Tracker app directly to SX900 via Bluetooth (BT)? Then it's clear why it didn't work: The integrated BT interface of the SX900 can only be used as an audio input (instead of the AUX IN jack), e.g. to play MP3s from the smartphone/tablet via the SX900 speakers.
To work with the Chord Tracker, however, you need a MIDI connection. If you want to go wireless, use a Bluetooth LE MIDI adapter on the SX900, like the Yamaha MD-BT01. Unfortunately, the firmware for this adapter has not been maintained by Yamaha for a long time. In the past, Yamaha even released a buggy firmware version that made the MD-BT01 unusable because it was automatically flashed with the UD-BT01 firmware. And Yamaha still doesn't offer a way to reinstall the correct firmware on the MD-BT01.
I therefore recommend using a BT LE MIDI adapter from CME (called "WIDI"), e.g. "WIDI Master" or "WIDI Jack").
Or you can use a USB cable connection (USB type AB cable, connected to the SX's USB to Host terminal). In order to connect the USB A plug of this cable to an Android smartphone/tablet, a so-called "OTG" adapter is required (USB A socket > USB C or Micro USB plug). With an iPhone/iPad, you use a so-called USB camera adapter instead (preferably one that has a USB A socket as well as a Lightning / USB C socket for simultaneous power supply of the iPhone/iPad.
Hope this helps!
Best regards,
Chris
