Synthesizer problem with handoff of sustained note to another voice

In the attached example, I have a horn note sustained over multiple bars, then switched over to another voice on a different staff with an overlap in time. The sustain is created with successive ties, each note tied to the next. The first voice sounds over the indicated duration, but the second-voice continuation does not sound. If I switch the second voice to a different pitch, it sounds.

Is there a better way to do this - say with successive slurs instead of ties? If two notes of the same pitch are connected with a slur instead of a tie (I haven't tried it yet), I'm concerned that there may be a phase discontinuity that will sound as a distinct attack on the second note.

Thanks in advance for any helpful responses.