Prove the backup rig will open the show

A plugin that lives on the A rig and not the B rig is a single point of failure that nothing warns you about. The file opens fine on the machine you programmed it on.

A professional playback rig is two identical computers, and "identical" is a claim somebody has to keep true by hand. The A rig gets the programming, the rebuild after the drive swap, the plugin the MD asked for at production rehearsals. The B rig gets cloned, rsynced, or built from a list written at 2am.

Then one thing does not make the trip. Nothing tells you. The show file looks correct on both machines, and the only thing that reveals the gap is Live opening it, which on the B rig happens for the first time at the moment you needed the B rig.

Sessions answers that question in the week before instead. Both checks below are free, neither one needs Live running, and neither one writes to your show file.

Collect All and Save does not cover this

Worth saying early, because it is the assumption that lets the gap through. Collect All and Save copies audio and video into Samples › Collected and Max for Live devices into Presets. It does not copy third-party plugins, and it cannot: Ableton's own documentation says plainly that plugins have to be installed separately on each computer.

So a set that was collected and saved, zipped, and moved to the B rig is complete in every respect except the one that will stop the show. The audio travelled. The plugins did not, and nothing in that process told you which ones mattered.

Two checks. Both free.

Point it at the show file

Drop the .als on Sessions and it names every third-party plugin the set calls for, then says which of those are not installed on the machine you are standing at. Run it on B. It reads the file directly, so Live does not have to be open and the set does not have to live on that drive. Stock Live devices are listed separately and never counted against you, because they are not a risk.

Diff the two machines outright

A Plugin Passport is the entire plugin inventory of one computer, exported as a single file. Export it on A, open it on B, and you get three lists: what both machines have, what only A has, and what only B has. That is the parity check, and it needs no show file at all, so you can run it the day you finish building B and again after anything that touched A.

You can try the reading half right now, with nothing installed. Our in-browser checker opens an .als in the page and lists what the set asks for. It cannot say what is missing, because a web page does not get to look at your plugin folders. That is the half the app does.

What it does not check

Worth being blunt about, because a check you trust for the wrong thing is worse than no check at all.

Plugins, not licences. It sees that the plugin is installed. It cannot see whether the iLok is in the other laptop.
Names and major versions, not point releases. It knows that Serum 2 does not satisfy a set built on Serum 1. It does not know that A is on 1.365 and B is on 1.36.
Not samples. Missing audio is a different failure with a different fix, and Sessions tracks it separately. More on that.
Not Live itself. Version, edition, Max for Live, Packs and hardware are still yours to match.
Ableton only. This check reads .als files. Sessions manages ten DAWs, but it only checks this one.
Not a substitute for opening the file on B. Nothing is. This is the check you run first, so the one you run last has nothing left to find.

The other half of the job

A tour is not one show file. It is versions of it, plus the rehearsal sets, plus the sets from the last three tours you might still need a stem out of, spread over drives and named by whoever happened to be awake.

Sessions is a library for exactly that. Every set on every drive in one list, with its tempo, its length, its key, the Live version that wrote it and a notes field, all searchable without opening anything. Collections keep artists and tours apart. It plays the bounce next to the set, so you can hear which version you are looking at rather than guessing from the filename.

The app is a free download and does the above on the free tier. Pro is $44 once, not a subscription, and one licence covers more than one computer. The EULA has the exact number.

What this is not

Sessions does not run your show. It is not a setlist device, it triggers nothing, and it belongs nowhere near your outputs. That job is done properly by the tools this world already trusts, and we are not pretending to be one of them.

Sessions is what you use in the week before, when the questions are "will this open" and "where did that set go."

Rig questions

Do both computers need the same plugins to open an Ableton set?

Yes. Ableton's own documentation is blunt about it: plugins cannot be copied into a Project folder, they have to be installed separately on each computer. A set opens with holes in it if the machine it opens on is missing something it calls for, and nothing warns you in advance.

Does Collect All and Save include my plugins?

No. Collect All and Save copies audio and video into Samples then Collected, and Max for Live devices into Presets. Third-party plugins are not collected and cannot be. This is the single most common reason a set that was collected and saved still fails to open properly on a second machine.

How do I check a backup machine has everything before a show?

Two ways, both free in Saltado Sessions. Point it at the show file on the backup machine and it names every third-party plugin the set calls for and which of them are not installed there. Or export a Plugin Passport on the A rig, open it on the B rig, and get three lists: what both have, what only A has, and what only B has. The second needs no show file, so you can run it the day you finish building the backup.

Will a set built on Serum 1 open if the backup machine has Serum 2?

No, and the check refuses that match on purpose. A major version is a different plugin as far as the set is concerned. What the check does not catch is a point release difference, so it will not tell you that one machine is on 1.365 and the other on 1.36.

Can I avoid the problem instead of checking for it?

Partly, and it is worth doing for anything you hand to a rig you do not control. Freeze and Flatten, or Bounce in Live 12, turns a processed track into plain audio, and audio needs no plugin to play back. You lose the ability to change the sound, which is why it suits stems and support-band rigs more than a show you are still adjusting at soundcheck.

Does it check for missing samples as well?

Not in this check. Missing audio is a different failure with a different fix, and Saltado Sessions tracks it separately. Collect All and Save does handle audio properly, which is why plugins are the half that catches people out.

Get Sessions All features Check a file in your browser

Sessions runs on your own machine. It needs no account, sends nothing anywhere, and works with no internet at all, which is the only sane shape for something you would put on a rig.