Once you get your drum tracks down, you can start building the song, track by track. Lay down the bass directly into Pro Tools, followed by guitar, keyboards, vocals, back-up vocals, glasses filled with water, a vacuum cleaner, butterfly wings, keys jingling — you name it. Here's a tip from our experience: Don't worry if your tracks “red-line” a little bit. This is supposed to be a big digital no-no, but we suggest just using your ears. If you hear crackling, adjust your levels.