Rallentando

Here is track that start at something like 120 BPM and slowly decrease to something like 80 BPM. I do not know how  what software they use to dom that. I'm pretty sure you can do that with Qlab 4.

Can some one could help me on that ?

Thanks a lot !

Your link didn't have any audio but the basic principle is shown above/ preserve pitch and fade rate to 80/120. i.e 0.66666666

But that's nearly half speed, so depending on your source material it's going to have  quite audible artefacts.

There are plugins .g Serato, Melodyne etc. that can do this, but only if you know exactly where the rallentando is going to occur.

Mic

It will sound like the attached video i.e a bit stretchy

Mic

Thanks a lot Mic !