I know you need two tracks with the MD. But I am pretty sure the OT can pull it off. I could be wrong. I have not dug into the midi side of the OT much, yet.
Edit: The setting is in the ARP menu. From the manual:
LEG controls the legato of the arpeggiator. This setting will affect the note trigs of the track even if the MODE setting is set to OFF.
• ON will play overlapping notes legato, releasing the old note after the new one. The NLEN setting adjusts the length of the notes when the arpeggiator is activated. If not activated the LEN setting will adjust the length of the notes.
• OFF will send out a MIDI note off message before the start of each arpeggiated note.
I have read that section from the manual over and over in an attempt to get the legato function to work with the arp on. I guess I need it said another way…I do not understand.