I've not heard the term "scratch tracks" before
Perhaps a better known term in certain quarters is a guide track. I must admit, I only came across the term "scratch track" when I first began frequenting HR.com.
A scratch track is garbage, that's why they call it a scratch track.
In principle, I agree with that entirely. But sometimes, the scratch/guide just has that
something that demands that it be kept. Two recent examples spring to mind, in one, "
The buttons of Z'iisquasha", I just wanted to get the drums down so while my mate played them, I played an electro acoustic guitar plugged straight into the DAW so that there'd be no spillage on the drum tracks. I utterly hate the sound of the Ozark electro acoustic plugged straight in. I've never liked it in the 24 years I've had it. It's awful and thin and when we'd done the take, there was nothing outstanding about it. The song wasn't even meant to have guitar in it, it was there literally as a melodic and rhythmic guide { the track notes even have it down as "guide guitar"} and so I never thought about it as being part of the song. It wasn't until another mate had laid down a harpsichord and clarinet part and I'd put down a bass part and I was about to wipe the guide guitar after I'd done the vocal that I thought that put opposite the harpsichord, it sounded ok, even though on it's own it sounds horrible. So I kept it.
On a track called "Bebe Shonga" I was again just capturing the drums and I just used my DI'd bass as a guide because I'd just bought a double bass and wanted to use that on the song but I was out of practice as I hadn't used one in nearly 10 years and besides, even though it was a quiet song, I didn't want any drum spillage on the double bass track. But even when just doing guides, the overall feel is very important to me, that intangible
something that will determine for me whether "yeah, this is the keeper" will show itself in the way the drummer/percussionist and myself have interracted. And in "Bebe Shonga", it was there in our take. Even as everything else was added, the bass always felt just perfect and I agonized for 4 months whether to keep it or not. But in the end I convinced myself that the original concept stood and it had to be a double bass so I laid down the double bass and wiped the bass guitar.
And I regret it ! I should have kept the guide bass.
So while most of the time my guide tracks get canned {for example, I'll use DI electric guitar guides for parts that are going to be acoustic because after 17 years of drums crowding my acoustic guitar tracks, I'd had enough ! } once everything is tracked or once the keeper has replaced the guide, once in a while, the guide just fits so well that there's no point trying to better it.