On my mz-r909, if you press down the upper-right corner of the lid with a disc inside, you can play from and record to the disc without closing the lid. If you let go of the lid, it will open and the disc will pop out, and if you're recording, the open-lock will be released too. Obviously, no TOC data will be written either.
I'm not sure if this is actually useful for anyone, but suppose you want to record something live that probably won't succeed on the first try, like a rehearsal or something. So instead of starting to record -> band botches up -> stop recording -> erase track -> wait for TOC update -> start record.. etc. you can just:
1. insert disc
2. press down the corner
3. start recording
4. band didn't get it right -> release lid
5. insert disc -> press down corner
6. start recording
7. repeat, ad nauseum
Now, since the Sony MD's will start recording immediately when you slide the record switch, it'll only take a few seconds to bail out and start a new recording. If you want to continue recording normally, just close the lid completely.
This seems to work on my n10 too, but not as smoothly.