So I got Duke of Bows & the violin is just a shame. My sim got to master the skill, but there are no achievements for the skill. Worse, no matter the skill level, the amount of simoleons she gets for performing for tip is always the same, making the guitar the best musical instrument in the entire game. To make it even more frustrating, the "perform for tip" interaction will only lasts for 3 sim hours whereas the other musical instruments "perform for tip" will keep going until you tell them to stop or the sim themselves needs to go to the toilet, hungry or going home.

Are there any mods out there that makes violin worth spending time on?

The only thing that comes to mind is the Variable Career Metrics mod by kidhedera here on modthesims.
It makes it so that the violin can become a skill requirement in a couple of careers.

You can do it yourself.

The resource is called "Violin_0x..." (there's also "Violin+Play..."). You have to... oh, forget it, I'll do it for you.

Extract the archive and put the .package file in your Mods/Packages folder
(extra TIP: put it in a sub-folder where you temporarily store new things
or stuff you haven't yet verified if work correctly).

The package, as is, contains exact copies of the game resources, so you'll notice no difference.
Open it with S3PE and edit the resources to tweak the settings to your licking (right click on them and select notepad).

Be careful of what you modify, don't touch anything that doesn't have a clear meaning.
You have to change the values you see between "".
For example, to raise the tips:

Do the same with kMaxTipPerLevel (with bigger values of course).

When you are done, save the file, close notepad, commit changes and save the package.

Double thanks for also teaching me how to use SimsPE.
What about the Perform For Tip? Or do I just change the kPlayDuration value? Just making sure I wouldn't break anything.

Awesome, this mod will definitely wants me to bloat all of my save games by pushing all of the sims to master the arts! :D

I don't understand the question. You mean kLevelToPlayForTips?
That indicates at what level of the violin skill the Play for Tips interaction becomes available.
Or you mean if kPlayDuration also affects the duration of Perform for Tips? I guess so, let me check... yep, so it seems.

Yeah, that's what I meant. Sorry I wasn't being clear. I tweaked the numbers based on what you told me, and she gets tipped 20 simoleons more than usual. Still not like the guitar but at least my violins won't need to scrape the barrel anymore. My problem was that the "Perform for tips" still cancels itself instead of just keep going & going like any other instruments.

This 1 is minor, I guess. But sims don't pay attention to the violin as much as they would to the guitar.

# But sims don't pay attention to the violin as much as they would to the guitar.

That's weird because, unless I'm missing something, watching the violin is an interaction
more advertised than watching the guitar, 80 vs 25 fun, there are other factors but this
seems to be the main one.

Maybe raising the fun faster will get that motive full sooner so they watch a Sim playing the
violin for less time than they watch a Sim playing a guitar. It's not like they stop watching
when the motive is full and the Sim is still playing.

The way tips are given may also be different (guitar and other band instrument all use the
same, while the violin has its own system), but I haven't examined that.

I trained a sim in guitar & a violin. When she played a guitar, all the sims in the area will come & watch. If she played a violin, only 3-4 at max, and the rest will just do whatever they are doing.