My only foray into Christmas tree light fun and games originated in the days of filament only globes wired in series for plugging directly into the mains supply.
The first set I remember had a string of globes rated for 17V. They had a screw base and, from memory, were about 5cm or so long (it's been a while). These were in the days of, if one globe failed, the whole string went dark. Chasing down the faulty globe was THE Christmas ritual nobody liked (I didn't buy my first multimeter until some years later).
In the early days, flashing lights consisted of one "special" globe that, when fitted, would make the whole string flash. Yes ... bang - bang. All on, all off. It was quite dramatic - and in those days, a cool feature.
We then got an "aluminium" Christmas tree - tripod base, wooden pole trunk with angled holes and steel rod branches with fringe cut "aluminium" (more like a metallised plastic sheet, I reckon) spiral wrapped around them for the leaves. It was very pretty, albeit completely inorganic, but not the place to run a string of lights that came with a 240V risk, so the old lights were draped over a timber slat divider, well away from danger.
Anyway, I had an idea.
I purchased a set of 20 lights - again full mains operation - and confirmed a series connection of all the globes, which indicated they operated at 12V.
First step was to cut off the mains plug and toss it. I then ran a length of 2 conductor cable down the string and joined each conductor alternately to the light string, resulting in 20 globes wired in parallel. I now had a 12V set. Connect this up to a 12V transformer and the electrocution risk was gone. Care was taken to prevent any wayward "leaves" being a problem and over the years, there never was one - even though I did a spiral wrap with some thin tinsel to keep the wiring together and camouflaged.
This configuration had another benefit.
The bang-bang flashing behaviour could now be tamed. By replacing a normal globe with a flashing globe, only that one globe would flash. With my new setup, I had 3 flashing globes, so I was able to set up the string so that most of the globes were on full time and only 3 globes were flashing - and they were flashing at different rates, so that after a minute of operation, they were so out of step, the result was random twinkling. This was so much more appealing.
A year or two later, I did a similar thing with a string of 40, wiring them as 20 lots of two 6V globes in series, again working from 12V.