1. The first thing you'll need to decide is which computer you're going to use, and how you want to use it: by replacing the current operating system, by adding a linux operating system along side what's already on the disk, or by utilizing a USB stick with a linux audio production distro, thereby leaving the computer unchanged. If you decide to remove the current operating system, be sure you have saved any important data in another place, as it will be permanently lost when the system is erased. (If you utilize a USB stick distro, make sure that it has the ability to save your work somewhere. You will have to use the entire stick. Make sure it has enough memory, and make sure you format it to the correct format required for the distro you want to use.)
There are lots of versions of linux. Some are lightweight, others not so light. Some are new, others have been around for years. Many are dedicated to doing specific tasks. And some of these have been designed for the purpose of audio (and sometimes video) production. You can browse different distros (versions) and even see their daily popularity ranking, and search for distros of a particular category, at Distrowatch.
2. Once you have decided which distro you'd like to use, download the image (maybe 15-20 minutes to download) as well as the md5sum file. You'll need to have a blank CD-R or DVD-R disc available.
When the image is saved to your computer, open your disc burning application (ie. Nero) and select the image. (It has an .iso file extension.) This file includes a code that should be visible in the disc burning application somewhere. This code is the md5sum number, and must match the md5sum file you downloaded. (If you cannot get the code from the disc burning application, you can try doing the install anyway; if the install is successful everything should be fine.)
So now you will need to write the image to the disc. It is NOT to be copied to the CD or DVD. You must burn the image to the disc using the "burn image to disc" option. This also will take some time (10-20 minutes). Use the slowest write speed possible, as this minimizes the risk of write errors. When finished, the disc should eject automatically, and you now have a linux distro ready to try as a demo, and install to your hard drive! :)
3. With the disc made, insert it in the computer and reboot. If it doesn't start the disc, you will need to reboot and enter in the BIOS control area, to set your computer so that it will read the CD/DVD drive before anything else. If it is already set, you should see some type of welcome screen for your distro. Depending on the distro, you may have several options to choose from. The default choice (if you choose none within the first few seconds) is to run a demo version of the distro, without actually installing it to the computer. This gives the user a chance to see what it looks like, try out some applications, etc. There is also probably an "install now" button somewhere on the desktop. If you don't want to install it to the hard drive, just shutdown the computer when you're done, and the disc will be ejected automatically. If you want to install it, click the appropriate button and follow the instructions.
4. If you want to install the distro, you'll need to decide whether to remove the current operating system(s) or not. Depending on the distro, there is usually a step in the installation process that gives you the choice of what to do. Remember that if you decide to erase your current operating system(s) you will lose all data as well, so save your data first!
During installation, you'll be required to choose a username (6-8 characters, all small case, no spaces) and a password. You may also need to specify a "root password." Make note of these passwords, they are very important!!
In addition, and depending on the distro, you may be given the option to select specific packages to be added. Ubuntu Studio has a thorough list of audio and video applications that can be selected during installation. (They can be install later on, if preferred.) You may also be asked if you want to have a realtime or low-latency kernel installed, if you are wanting an audio-production set-up. Choosing either of these means that your computer will give higher priority to applications that are used for audio production. This serves to improve performance, quality of recordings, etc.
When the installation is finished, the disc should automatically eject, and the computer should automatically reboot.
5. When the computer reboots, you'll then be able to set up things the way you want them, and install applications the way you want them. The first thing to do though is to check for updates, since there have probably been important updates made available for your system since the distro was released. To do this, you should have an application in the menu (under "system" usually) called "Synaptic Package Manager." You will be asked for your password when you open it. When opened, click the "reload" button and wait for the repositories to update. Then click "mark all upgrades." The packages that are listed in the small window at this point, are all trustable package updates that can be installed. Confirm by clicking "mark." Then click the "apply" button and finally, click "apply" in the pop-up window. Let the Package Manager download and install all the updates. When finished, you can close the window. You will probably be asked to reboot, if many upgrades have been done. (You might see an indicator in the desktop panel bar telling you to reboot.)
6. After this reboot, your computer should now be up-to-date. Browse your menu to see the apps that are installed. An important application for making music with linux is an audio manager called "Jack." You may find an application in the audio/video section of the menu called "QJackCtl." (If not, just open Synaptic again, type in QJackCtl and click search. It will appear listed, along with any other apps that contain that same name. Click the checkbox and select "install." It will tell you that there are other applications that must be installed with it, so agree to install those as well. Then click "apply" and again "apply" in the window. The entire installation and set-up of QJackCtl will be done for you.) If you had to install QJackCtl in Synaptic, then this is when your system will ask you if you wish to install a low-latency or realtime kernel. If you choose not to, you can always install one later. If you want to see an amazing complete "overhaul" of a PC system including the kernel, all in "just" 4 pages of a forum discussion, click HERE.
Along with QJackCtl, you'll want to install (in Synaptic again) a file called "a2jmidid" (without the quotes). This file will make sure that applications running on the Alsa audio manager will be sent into Jack. When a2jmidid is installed, then open QJackCtl and click on the set-up button on the right side of the panel. Click the "options" tab and type in the space where you see "execute script after start up" the following:
a2jmidid -e &. After this, return to the first tab, where you can adjust your audio settings (sample rate, etc). When finished, you'll need to click "stop" on the main window, and "quit." Then re-open QJackCtl again with your new settings made.
Most music production applications these days use Jack for audio processing. Therefore, your sessions will start with opening Jack using QJackCtl. Then you can start your music applications. (There are also applications that allow you to save your set-up for future sessions.) There are several ways to connect instruments and applications by audio or by midi. You can click on the "connections" button on QJackCtl, or else use a separate application to control all your connections, such as Patchage.
Oh, one last thing. You may have heard that an anti-virus for linux is not necessary, and this is true. However, there is a very lightweight firewall available in Synaptic that is worth activating. It will never bother you or take up CPU. Just do a search in Synaptic for "ufw" (without quotes). Install it, then open a terminal and type
sudo ufw status. Type in your password (you won't see the password appear, for security) and hit enter. Then type
sudo ufw enable and hit return. Now your firewall should be enabled on startup, always. Nice! :)
For more start-up info that I may have glossed over, a good place to start is at: The Linux Musicians Wiki Page.