DGX670 - Selecting voices from MIDI tracks

[Major Minor]

I upgraded to the DGX670 from the DGX660 and I am trying to work out the best way to select the voices on songs I have bought or downloaded. At the moment, I am having to choose a voice rather than the voice that is loaded within the song. For example, let's say I want to silence the melody track. I would go to the score and then Set Up and then select the appropriate Right channel (1-16). But how do I get use the same voice that has been silenced? On the DGX660, all I needed to do was press the OTS button and the voice would be selected. The OTS link button on the DGX670 seems to function differently. Hopefully this makes sense.