Tempo track editor changes Midi but not Audio

I have been trying to produce a tempo reduction at the end of a piece which contains several instrument tracks using Halion SE midi data and just a single audio vocal track. The midi data responds as expected but the audio track tempo is unaffected. After applying the Tempo change with the tempo track editor, only the midi tracks are slightly longer (as expected) so I tried time stretching the audio track. This had the effect of creating progressively out of sync vocals from start to finish. The tempo reduction was only over the last four bars so it seemed logical to time stretch only those last four bars of vocal. I snipped the 4 bars out, time stretched it, then glued it back but it still didn’t sound quite in sync. There must be a better way of dealing with a mixture of midi and audio tracks in the tempo editor, surely??

I have done that early on–changed my mind about tempo after I recorded audio tracks–and ended up re-recording the audio. In other words, I found no way to match the audio with the midi, especially if the tempo is changing gradually over time. Of course, you can do brute force and snip the audio into syllables but that can cause artifacts, clicks.

Thanks Leon,
Re-recording the Audio was my backstop but it looks like it has just been promoted. The only alternative might be to mix down and then apply the tempo change. But if I don’t like what I hear, I end up doing a soft shoe shuffle between mix down and reprocessing until it sounds right.

Many thanks,