Okay, warning first: This Is A Rant!

I bought Pets shortly after Showtime, so when I started my first game in Appaloosa Plains SHT lots were already present (I haven't played in Starlight Shores at all so far). Of course the Coffeehouse had to be 25x32 thus occupying a 30x40 lot. No surprise there . But this is not the rant, I'm just trying to build up some suspense. In the beginning I was wise enough to remove them all, but later decided that it may actually be nice to have the Rodeo place (of course again an oddly sized lot) and the small Performance Park from the Library bin. But then all hell broke loose.
At first everything seemed fine. The game took two Sims from the pre-made homeless and made them proprietors. I was also quite happy that it chose one of those cowboys for the Rodeo place. How nice! A few days later my Sim got the message that a Simfest is going to happen at Rodeo Go-Go, an opportunity not to be missed, so I sent him there. There was an acrobat, a singer and a magician -- all taken from the homeless pool -- and they did what they were supposed to do: they performed. My Sims got various moodlets (remarkably enough he got the "saw an awful show" when everyone sent plus signs around and "saw an amazing show" when everyone booed), and left in a happy and entertained stage. Several days later, another Simfest at the same place. Everything went as before, I was only a little surprised that the performers were the former mixologists and bouncers of the Dive Bar and no trace of the previous set. In the meantime the staff at the bar was replaced with completely new Sims (you know the kind: dark skinned, obese, bright blonde hair with pirate hats). Well, no customised bar staff then anymore, I thought, who cares?
Now the third Simfest turned into a complete disaster: the stage was empty, the props were gone and the supposed performers stood in front of the stage, wearing swim suits and cheered an eternally dark and empty stage; the former proprietors were performers and the new proprietors were, you guessed it, dark skinned, obese and blindingly blonde.
I read that replacing the stage floor would fix the empty stage. So I did. Funnily enough, replacing the stage suddenly made some tables and chairs appear within those white squares. I swear they were not there before, and custom-CASTed, too! But the props were gone for good. Fine, I added some others and was just glad that I wasn't charged.
But onwards to my fourth Simfest. Location this time: The Park! When my Sim arrived the game had already eaten the props but at least granted me ONE performance by a totally new singer, who happened to be one of the obese mixologists from the dive bar. The others stood in front of the stage, and quite a lot of them too, blocking my Sim's access to view anything. I guess the squares were already full.
I then decided that I had seen enough and deleted the park during the night and turned the Rodeo place into a watering hole. Of course deleting the proprietor spot was only possible with cheats
And as a final result I now have 9 magicians, four singers and two acrobats in the homeless pool, a completely new set of bar staff and a serious Showtime trauma, and all this after only five weeks into the game.
And if anyone wonders why almost every night they hear this strange music, it's the game creating new performers and promoting the existing ones, endlessly increasing the pool of homeless Sims until your game explodes - and that is with Story Progression OFF.
Well done, EA, well done

I am kinda relieved to hear that it's an EA thing instead of a SP thing. I've had all my bouncers, cashiers and paparazzi turn into magicians and acrobats and I was blaming SP for it.

Lucky, I'm pretty sure that Overwatch can help manage the homeless Sims so the game won't explode.

I haven't experienced anything remotely similar to what is being described here, so I don't think this is an 'EA thing'. I did have the empty stage at the very first simfest, or invisible performers, whichever it is, but this was repaired permanently in all games I've started since then by replacing the stage where the first simfest occurred.

In all my games the first simfest performers are created either by immigration or possibly a few unemployed townies have been grabbed and assigned those jobs, or a combination of this. These same performers return for the next simfest, and the one following, etc. The proprietors are the same sims every day; none of these sims are swapping roles with one another, and certainly none of these are swapping roles with mixologists or bouncers.

Hm, interesting. So, your performers are residents? Maybe it is like that in my game because they're still all homeless? I know that I had the occasional role-swapping in Bridgeport, too, with only LN installed. And I had the performers role-swap constantly when I played Lunar Lakes with SHT installed but no SHT venues. True, the one magician that moved in after a while had remained a magician, but the homeless cycled through these professions and changed their levels from 1 to 10 and back to 1.

Edit: At the moment I'm running a completely vanilla game, in a default Appaloosa Plain, i.e. with Performance Park, the Karaoke place, a Coffeehouse, and the Warehouse. Story Progression is again off. Week 1: No Simfests yet, but three individual performances so far. 1st one went okay. Day 6: One of the Paparazzi decided she'd be happier as a magician and was replaced by Pudding Paparazzo. Day 6: the proprietor of the Coffeehouse turned up at the Warehouse as today's acrobat. She appeared in swim suit then changed into her everyday clothes and performed. Some Pudding is now the Coffeehouse proprietor. Week 2, day1: Paparazzo no. 2 is now a magician, too. During the night two jingles played: one denoting that someone has joined a profession, the other that someone got promoted in a profession. Accordingly on day 2: former-proprietor-now-acrobat is now a much better acrobat, although she vomits quite a lot when using the ring of fire. Maybe she should have remained a proprietor after all. Day 3: First Simfest at Performance Park: Mixologist no. 1 is now an acrobat and the proprietor of the Warehouse a magician, there's also a new magician I haven't seen before. Day 4: no shows but the magician who was the Warehouse proprietor changed her magician level twice. Day 5: Turned SP on and had a second Simfest, this time at the Karaoke place. Two former paparazzi are now performers, too, one of them is already one of the newly generated Sims that had replaced another paparazzo turned performer. Wekk 3, day 3: Another Simfest at the park. Greet a new acrobat, ex-paparazzo. SP has so far not moved in any of the performers. In fact it has only moved in one paparazza, killed 4 pets, one child, one teen and moved out two households, turned half the town into vampires and the other half into celebs.

I believe what you're describing is referred to in the gaming industry as "Working as intended". It's a mess-up on such a large scale that they do not want to admit they messed up so they just call the insanity normal. Some companies (lets say Blizzard) fix those "features" with quiet patches, some just pretend it was supposed to be this way from the start.

F.e. in the Sims base game, if you have too many Sims and some need to be killed off, the game will start with the most logical choice - the toddlers (oft drowning in pools). As much as I (you, he, any sane person) might be shocked by this, it is - "working as intended".

Music? Never noticed it because I always play with the sound off. My husband's usually in the room when I play so I'll mute my game so I can talk to him.

I know the music that you mean in the middle of the night. It annoys me cause I know it's not from my household.

I don't usually get Simfests in my town, but I have noticed that random sims will get hired for the jobs. It is really annoying.

I have a town that is completely empty, custom built very small, no building at all or inhabitants whatsoever. I use it whenever I want to do photo shoots of my sims, since it loads in like, 5 seconds. one day while doing a shoot, i noticed some random homeless townie doing magic tricks for tips in a far off lot.

So, in my current game I tried it again. After my singer had hit lvl 10 by exclusively peforming for tips and doing sing-a-grams, I added one live show venue to the world. This time I thought I'd be clever and added a family of four potential performers to the homeless pool - one acrobat, magician and singer and one undecided one. I also moved in an acrobat as a resident and created another unemployed homeless couple for potential proprietor and mixology duties. The town already had 4 LN bars that had a total of 4 mixologists, and a Salon with one tattoo artist and a resident as stylist.

- The first Simfest occurred and was introduced by that dreaded profession music: it had spawned two more performers, or rather, it had dragooned two of my mixologists into these professions. One of them showed up, the other didn't and I guess that's when my Sims cheered the empty stage. The local acrobat was not even there. OK, I thought, maybe the game needed more Sims, so I added two more homeless Sims to fill the two now vacant mixologist roles.
- After a few days I heard the professions music again and the message for another Simfest popped up. This time the victims were the tattoo artist and another mixologist. The former performers did not show up and now clog my pool of homeless Sims and my actives were cheering an empty stage. The former tattooist was present but did not perform. The former mixologist did not come. Accordingly, I added two more homeless Sims, one for the tattoo role, one for mixology.
- Simfest no. 3 kidnapped the new tattooist and another mixologist and the one undecided homeless that I had added in the beginning. NRaas SP had given her a job first but I made her quit that soon after. I think that none of them showed up at the Simfest and the stage remained empty save for the one resident acrobat and my active singer, who, btw, won the Simfest. After the Simfest I used MasterController to make the tattooist quit his magician career and he showed up as a tattooist the next day again, although he had lost his career outfit in the process and now works in his everyday clothes. For the mixologist I added another homeless Sim.
- The 4th Simfest created another performer initially. It was the wishing well lover that I had spawned two days before and whom NRaas SP had actually assigned to the culinary career. After the Simfest ended, SP immediately gave him a new job again, this time in journalism. During the Simfest I suddenly heard the profession music again and the last mixologist appeared as a magician but as her initial work shift was to start soon she entered the building changed into her bartender uniform and left the building again, and my Sims cheered an empty stage. I followed her and saw that she did not actually go to her bar but left the world then as an unemployed homeless Sim. Fortunately, she came back as a mixologist the next day.
- With Simfest no. 5 I was really lucky. It only dragooned one homeless who was a Sim that NRaas SP had retired shortly before and finally my magician I had created way back was there. The local acrobat performed, too, and I had one of my actives join. So no empty stage and no further hirings.

End results and assumptions:
1) The role manager and the performing careers manager do not really work very well together. Role Sims are easy prey for SHT careers and once hired it won't let them go. But this doesn't guarantee that they will create a steady stock for future Simfests.
2) Maybe this system will cool down once a certain number is reached. At least my last Simfest went smoothly when I had a total of 12 (!) performers, three residents and 9 homeless, 4 in each career. How many it will need if you place more than one venue, I don't even want to think about.
3) Empty stage syndrome might be caused by two things. First, the dragooned homeless fails to make an appearance, secondly, they may not have the appropriate level where the latter factor may also be the reason for the former.
4) The game assigns the levels randomly. This I learned thanks to NRaas SP's message system. A live show venue requires level 5 in a SHT profession, but not all of the homeless performers meet that requirement after being hired. This possibly creates the pressure to spawn a new performer.

The next thing to try would be a neighbourhood with a lot of resident performers. But, in all honesty, I don't feel like creating a circus encampment just to make sure that Simfests work properly. I'd rather say that my next game will be perfectly fine without so much as a single trace of any SHT venue.

Hopefully, this will not be considered double-posting, but as this thread turns out to be my personal monologue, I'll provide my update here:

Ok, I did what I said last time that I wouldn't do: I started a new town and created a circus encampment. As Setra had become unplayable after several Simweeks I moved the two performers (acrobat and magician, level 10 and 8 respectively) I had there into Appaloosa Plains. At first I wiped it clean of any SHT venues as I needed enough resident performers of an appropriate level first. I then created another family of 5 (2 singers, 1 magician, 1 acrobat and 1 with a proper job to prevent them from starving). So my game started with 6 resident performers.
As soon as my magician had hit level ten and the other 4 were level five and up, I added 1 Live Show venue and had most homeless Sims quit their jobs with MasterController. Simfests began to happen then once a week.

The first Simfests were the usual nuisance: instead of taking the resident performers they always used 1 homeless to stock up the pool of clowns. As I had enough unemployed homeless only two mixologists fell prey to the system and I ended up with 6 resident performers and something like 6 homeless ones. But at least no empty stage syndrome then.

At NRaas I read then a post by twallan that said that Simfests require 2 contestants in each category, and decided that I would have to have more residents then, as my own two would probably not count.
Therefore Appaloosa Plains had to welcome the additional influx of 3 more performers, one in each category. But as they were still level 1 the following Simfest still spawned new performers, and as the pool of homeless was now completely occupied it created new Sims (dark skinned with blond hair, as usual). No problem, I thought I can TA them afterwards if I want.

The Simfests themselves went rather smoothly. I had ensured that my two performers were always present and participated. The stage remained intact and all performers showed up.

The only Simfest that caused me grief was the one where I didn't send my own Sims. ErrorTrap reset the proprietor and this broke the stage: proprietor gone, props gone, audience tables gone, empty stage syndrome.
I had to replace the stage carpet and rebuild the stage. But this caused the next nuisance. The next day I had two proprietors. The old one and a completely fresh Sim (dark skin, blond hair). And both came regularly during the next days until I used MasterController and gave the old one a job.

In the meantime the 3 new resident clowns had reached level 5 and so I was looking forward to the next Simfest. And yes, thank the gods, no new performers spawning. Although not all residents were present, one of the homeless performers was there and so I had 2 singers, 2 acrobats, 2 magicians and my own two. Of course the game had then to decide that one of the acrobats will have to throw a party at home during the Simfest and after a while he errored out and ErrorTrap reset him . Apparently he tried to call a contestant autonomously and this had caused the error. Why he did that, no idea, and I still have to figure out how that is supposed to work anyway, because when I told my own Sim to do the same, the only ones I could challenge were those that were present on the lot. So why call them on the phone?

So, the result for now after some 10 weeks into the game: 15 (!) performers in a town with only one venue - 9 residents, 6 homeless, that's roughly 1/4 of the human population of Appaloosa Plains. And even if the spawning seems to have stopped by now there are still the other errors that can occur during Simfests and break everything in their course.

Verdict: A Messterpiece

I've had SHT since the day it came out and I've never had a successful Simfest, for exactly the reasons you've listed here. I've also never completed the Singing career without it degenerating into massive game ending glitches just after you get the...what is that thing? A portable lights display? That thing. The singer just freezes on stage as everyone cheers.

Showtime still exists on my machine SOLELY because I can't be bothered to uninstall it. What a waste of money.

I've had one successful simfest. After that it's been crap and NPC spam. I'm going to have to use Overwatch to start getting rid of the homeless, which I was trying to avoid.

Ha, indeed. Showtime currently occupies position 2 in my personal list of meh expansions, but it comes dangerously close to number 1, which is Generations.
Especially because both EPs have nice ideas but bork them to the point that it hurts.
Simfests could be so much better if, f.ex., they were like talent shows and every Sim could participate not just the professional attention seekers. I imagine that the fail levels this could produce would be so much more entertaining. And the rest of the days could be filled with gigs for actives and inactives and if there aren't enough professionals then let the stage be empty for a few days. The way it works now is that the venue IS empty six days a week and fills up with contestants for one day, and these have to be professionals and they have to be present and you get the same performances over and over again.

Also, why does my level 10 Vocal Legend sing Karaoke as if he had never seen a microphone in his life? Because karaoke is a separate skill

And why can't children watch the shows?

And why will nobody watch when my performers perform a trick unless they do it for tips?

Why can I use the props only on stage properly?

Why are my performers without any friends when they fail? The hit to relationships is out of any proportion compared to the effort it takes to get those friendship points back.

And why do they lose everything when they quit those careers? Can a magician suddenly not pull a coin anymore from someone's ear when they don't do this for money? Especially considering that all three careers have a special skill - a waste of skill records IMO. And I don't understand these skills anyway. My singer began to set himself on fire regularly after he had reached level 10 in both skill and career.

ETA: Oh and I almost forgot. Now as my town has enough performers to prevent the excessive spawning of homeless I notice that no other Sims show up during Simfests anymore. Only the performers are there now. Does this perhaps mean that the game counts the number of available seats (and each audience table carpet only holds two seats while occupying a 4x4 tile) ? If so I would have to enlarge the venue too, because now it feels a bit like a circle jerk.