When rendering a midi instrument (synthesizer), Renoise seems to ignore the legato of the synth patch somehow:
Original (how it should sound like, and how Renoise plays it, with legato):
http://cie-online.de/temp/rn/basslauf_original_with_legato.wav
Rendered (how renoise renders it, without legato):
http://cie-online.de/temp/rn/rendered_basslauf_no_legato.wav