You have a Mega Acousticbass on the S900 (Voice Nos. 008/0/017)
There is a choice of 7 slides available as far as I can find (checking out that voice on Ty3).
To trigger them you have to set the voice to the "correct" octave and play the 7 notes C5 to F#5.
To set the octave:
1. Make sure the keyboard octave is at default (zero)
2. Go to Tune tab of Mixing console and set the Octave for the voice to +1 (ie. 3 octaves up from its default setting)
Play the above keys and you should hear the slides.