I once own logic pro 9 on disk. Now I have a laptop that doesn't have a disk drive. I want to get back into music producing. What do I have to do? buy the software again?

To use Logic 10 you would need to buy the software again.

But to use Logic 9 I guess you need a Superdrive to install it from the CDs, bearing in mind that Logic 9 will not function on the latest OS, I believe El Capitan was the last compatible OS.

Good luck, i know a few people who swear by Logic 9.

If makes any difference, everyone who went from 9 to X had to buy it.

As we did from 8 to 9, 7 to 8, 6 to 7 and all the way back.

It does now cost less to buy it outright than it used to upgrade.

There have been no further costs once Logic X was purchased. That's no additional cost since 2013, which is pretty cool.

Totally agree with the two replies above.

Just a little correction: if you still have Logic Pro 9 installation DVDs, all you need is any portable DVD-drive to install it, not necessarily Superdrive. Also, if you have a powerful enough Mac, you can run a legacy Mac OSX (and LP9) in a virtual machine, using VM software like VirtualBox, or similar.

That being said, though, it's totally worth it to switch to current Logic Pro. It costs less and packs more. I personally like the new genre-oriented loop packs. Plus, it allows to download all legacy sound content for compatibility with projects created with earlier versions.