Hello everyone and happy new year, i have few songs that i have composed with platinum i used soft synth, i wanted to put them together so that they can play back to back , of course each song have their own instruments and tempo so how do i put them together and have them play correctly with their original settings?? Thank you

You could mix each song down to a WAV (or MP3, if you prefer), then open a new project in your DAW with two audio tracks.  Put the first song on 1 audio channel and the second song on the other. Push the second song to the time you want it to start (you can even use automation to crossfade the first into the second).  Then bounce them to another WAV or MP3 which should yield both songs, one after another.
Hope this helps you.
 
John B

Another way would be to create a blank project, then drag each of your old projects from the Media Browser into your new project:

Using a Playlist?

msmcleod
Another way would be to create a blank project, then drag each of your old projects from the Media Browser into your new project:

WOW!  you just might have opened a whole new world to me!!