That is IF they sound any different, I personally only had Atari modified drives so apart from the step being faster they sounded all the same?
And IF they do have sounds would the inclusion of the sounds make the exe bigger than you want?
The rotation sound doesn't have or really need variants per drive, though I need to try to make a better sample. The current one doesn't loop cleanly and sounds somewhat like a washing machine. Actual drive rotation sounds have two parts, the motor and the disk; the disk sound runs at rotation speed (288 RPM) and can be fairly loud depending on how crappily made the disk is and whether it has a loud wiping sound as the media rotates. Some were so loud it sounded more like your disk was being sanded than read. The motor sound is intentionally louder in Altirra, though, so you can hear it; the 1050's motor sound is barely audible.
The step sound mainly comes from the mechanism, so yeah, besides step rate 810s and 1050s should sound similar. Though I have heard that even those drives sometimes shipped with more than one kind of mechanism. The stock 810 seeks so fast that the actual sound doesn't matter much except when the head is bumping against the track 0 head and effectively stepping at half speed; the 1050 and XF551 sounds matter a lot more since the step rate is a lot lower. There are several videos of an Indus GT on YouTube, and that definitely sounds more clattery than what I've got hooked up, though that could be due to the mic being so close to the front of the drive.
Size isn't really an issue as the samples are really short (20ms or less) and they could be stored more compactly. Besides having the sounds available, the main issue is getting a clean enough sample, which is especially difficult given that some drives almost never do a single isolated step and it's very easy to get a lot of noise into the recording. If anyone's got one of the weirder emulated drives and wants to help get representative sounds in, I'd be happy to give it a shot.
As a side note, disk drives can also make different step sounds depending on whether they're nearer to the inside or outside of the disk. This isn't that noticeable on the 5.25" drives, which is why I haven't bothered. However, it was really noticeable on 3.5" Amiga drives, and therefore also the lack of variation when WinUAE used a uniform step sound. I'll never forget the "uh-uh, uh-uh" sound that basically signified that your disk was not readable....
Forgive this newbie question, despite all my years around Atari's I never had a non Atari drive, they were mega expensive here and my 810 and 1050's did what I needed with the mods in, so now with these Percoms etc do they work as boot drives, I loaded up Mydos with the Percom being D2: and formatted a disk which it recognised, set the density to 2D and played with Altirra to make a DD disk etc, don't know if it was right but it seemed to work but can these boot (nothing I've thrown at it so far) or were they an additional data drive only?
Yes, the Percom can boot double density. You need it to be D1:, obviously, and also the disk to be inited with a DOS that can boot double density. Any DOS+disk combination that can use double density should also be able to boot off of it... well, exception being SpartaDOS X of course, since it doesn't actually boot off of the disk. But yeah, I know what you mean. Growing up I only had 810s, so I hadn't even experienced 1050 enhanced density until I started emulating, and even now I still don't actually have a physical double density capable drive. After emulating a few of the more oddball ones, though, I'd gladly use one of the enhanced 1050s over the others since most of them failed at either or both of density detection and high-speed operation.