Even with the track volume turned all the way up, the green bar barely showed, no matter how hard I pounded on the keyboard. Naturally, I turned to Google to solve this problem. I found a lot of old, irrelevant advice. The closest thing to good information I found was this FAQ page (warning: do not click unless you've got a good pop-up blocker), clearly geared toward an old version of GarageBand.
But that old info pointed me in the right direction, and I found the answer. Here's how to get it to work.
- With your MIDI controller (i.e. keyboard) plugged in, select the MIDI track in GarageBand.
- Over on the right, select the Edit tab, highlighted here in yellow.
- From the Visual EQ dropdown list (also highlighted in yellow), select the Manual option.
- A pop-up window like you see on the left here will appear. Click and drag on the blue line to increase the volume.
The settings you see here aren't necessarily the best - play around with it until you get something you like. It might vary depending on the instrument you're using. For example, I needed to raise the Bass and Low Mid to increase my overall volume, but didn't touch the Treble or High Mid. (My keyboard's all about that bass, no treble.)
I rushed to take a screenshot and post it here so that anyone else out there using an old MIDI keyboard with a new copy of GarageBand would be able to find this information. If you actually know something about MIDI controllers and EQ's and all that jazz, please post in the comments and correct any mistakes I might have made. Thanks, and happy music-making!