Hi Marco,
Calling up Voices other than the Panel Voices is described in the Tyros5 Reference Manual on page 6 ("Selecting GM, XG and Other Voices"):
1 Press the PART SELECT button corresponding to the Part you want to use (Right1, 2, 3 or Left)
2 Press one of the VOICE category selection buttons (other than the [ORGAN WORLD], [ENSEMBLE] and [EXPANSION/USER] buttons) to call up the Voice Selection display.
3 Press the upper [8] button (= "UP") to call up the Voice category folders.
4 Press the upper [2] button (= "P2") to display Page 2.
5 Press the desired [A]–[J] button to call up the Voice Selection display of GM&XG Voices, GM2 Voices, etc.
Note: You can also find the “Legacy” folder in this display. This folder contains previous Yamaha keyboards’ Voices (such as Tyros, Tyros2, Tyros3, Tyros4, etc.) for data compatibility with other models.
6 Select the desired Voice.
Please note that you can also select Mega Voices in the same way as described. However, these are not suitable for playing in keyboard parts, but only for use in Styles or MIDI files. (With Mega Voices, the sound result depends primarily on the velocity.) For the sake of completeness, you COULD limit the "Touch Sensitivity" (e.g. in the VOICE SET) so that you could still play Mega Voices live. However, I recommend that you only do this in exceptional cases.
Hope this helps!
Best regards,
Chris