I hope I am wrong, but it appears that, unlike the 770, there is no live control for volume. It has the VH instead.

Balance/Song,Audio Adjusts the volume balance between the Song and Audio playback.
Rotating the knob to the left increases the Song volume, while rotating it
to the right increases the Audio (USB Audio Player) volume.
Balance/Song,AUX Adjusts the volume balance between the Song playback and sound input
from the [AUX IN] jack. Rotating the knob to the left increases the Song
playback volume, while rotating it to the right increases the input volume
from the [AUX IN] jack.
Balance/MIDI,AudioAUX Adjusts the volume balance between the playback of MIDI data (Song,
Style, Multi Pad) and Audio (USB Audio Player and input from the
[AUX IN] jack). Rotating the knob to the left increases the MIDI volume,
while rotating it to the right increases the Audio volume.
Filter/Voice,Style Adjusts the cutoff frequency of the filter and the resonance for all keyboard
parts and the Style to change the timbre or tone of the sound.
Reverb/Voice,Style Adjusts the Reverb depth for all keyboard parts and the Style. Rotating
the knob to the right makes it deeper.
Chorus/Voice,Style Adjusts the Chorus depth for all keyboard parts and the Style. Rotating
the knob to the right makes it deeper.
Master Tempo Changes the tempo of the currently selected Style or Song. Rotating the
knob to the left makes it slower, while rotating it to the right makes it
faster. Setting range is from 50% of the default tempo value to 150%.

Thanks for the reply Donny. I have tried all combinations and nothing works. However, the sound is really good on my SMFs from my SD2 to the aux in. I will control from module.

Bernie I sometimes use an INLINE Vol control works well also...

Thanks, I have one but the slider on the SD2 is handier. No problem.

Bernie I just had some time to test this on my S970 and it works perfectly...
YES you can assign the LIVE KNOBS to control the AUX Volume of a LT, Phone, Mp3 Player, etc, as shown here, ...open your live knob menu scroll down to AUX Volume & push assign,...that's it.
A great feature.

enjoy

Hi Donny

Very nice of you to follow up. I posted the question on the Yamaha forum and subsequently found the answer for myself. I didn't realize that when you press assign(in the window) that a whole bunch of additional options open up. I didn't think to post back here.

I too think it works great.
Thank you

Good to hear Bernie ....yes the Live Knobs are a powerful feature for the player for sure,.....with the Now S970 I dont need to use a mixer anymore as I can control the LT Vol & Voc Mic Vol with ease independently 1&2 .....