Hi Toril S,
"Panel Sustain" and "Sustain Pedal" do completely different things:
When you press the Panel Sustain button, the value of the Voice Set parameter "RELES." (= Release Time) is temporarily increased. This means, the time from releasing the key(s) until the sound "dies down" is prolonged/extended. So you could also leave the Panel Sustain button OFF, but increase the value of "RELES." slightly.
You can determine the Sustain Level applied to the edited voice when the VOICE EFFECT [SUSTAIN] button ("Panel Sustain") on the panel is turned on:
Go to VOICE SET of the desired voice, tab to EFFECT / EQ Page and go to 1 REVERB DEPTH / CHORUS DEPTH / DSP DEPTH / PANEL SUSTAIN.
The Sustain Pedal works completely different. The only thing it does is: When the Pedal is pressed, the voice sounds exactly as if the key(s) were pressed all the time. In certain limits, you can try to adjust (increase) the "DECAY" parameter (= Decay Time) in Voice Set. This parameter determines how quickly the sound reaches its Sustain Level (a slightly lower level than maximum). The lower the value, the quicker the Decay.
Please refer to pages 14/15 in Tyros5 Reference Manual (section "Voice Set" is starting on page 11).
Hope this helps!
Best regards,
Chris