About the marimba, I play hammered dulcimer with my wife: its fun to make music while beating on a thing.  I worked up "Irish washerwoman" to about 160 bpm; it wasn't musical like that, but it was fun.
"wowing audiences": when you're working 6 nights a week and your booking agent says he can get $100 more a night if you do this or that, you then make the choice.
I can still remember in Illinois, a jazz bassist set in with us.  He and I took off together on rhythms for 15 minutes.  It was fun.
concerning vibrato: I'm thinking of the French singer, Edith Piaf. I've always liked her sound, but  you are right about high opera types ruining music.
And about eminor: music is art.  To have someone tell you how YOUR art is supposed to sound is just wrong.  Like saying "Whiter shade of pale" has too many chord changes.

MrYikes said
........................... And about eminor: music is art.  To have someone tell you how YOUR art is supposed to sound is just wrong.  Like saying "Whiter shade of pale" has too many chord changes.  

I fully agree, but maybe I wasn't clear enough in explaining what I actually meant. Ideas about distinguished characters and mood the keys or scales would contain where very popular. Composers of the past might have felt the need to consider these ideas to not disappoint the audience. You probably know how people are: they expect what they're used  to.

Wikipedia emphasizes there have always been doubts these ideas are true. It might be just imagination like pseudo-religious apparitions. The more people believe it, the more it's considered true. With meantone temperament there where tonal differences, but not in modern equal temperament. At the keyboard I'm simply to dumb to accompany in F♯ major, but I can play just F major and transpose the whole instrument half a note higher. I did something like that with an F minor movement by Telemann on a MusicPartner play-along: it would be a pain in the neck to already improvise over F minor, so I transposed it to E minor via NERO WAVE Editor. So does it now suddenly express sadness and pain?

I don't think the author Johann Mattheson (Handel's friend during their Hamburger time) really believes in those characterizations of keys/scales. He just explains the traditional perception. Anyway, if I rave on Edition Peters' Telemann, Handel and Bach basso continuo play-alongs I consider it training my ear and technical abilities. To many worshipers of the old masters this means just an infamy.

Nonetheless I'm sure the tone of the violin sound differs in keys. In C major you have lots of open strings—not so in A♭ major. Anyway it seems to me the color changes if I have to involve many D♭, A♭, and E♭.

See, 434 Hz—why not? That's why 'absolute hearing' is nothing but vane bias. If there was a button at my head, to adjust the pitch in cent steps, it would be useful. And how about little indicators in my eyes, so I can pitch my violin while looking into the mirror ...

Dancing to Take Five? Dancing was one of my jobs in our swingtett. We did not only play in jazz clubs and at times our listeners were far from being jazz fans. I remember a gig in 1987—the audience was talking, looking at their beer, completely behaving like there was no band on the bandstand. These were the moments when our guitar player reminded me, "Looks like you have to tap once more...." Over the years I learned, my old tap teacher was right, who liked modern dance better because tap is stupid—very difficult to learn, but stupid. People like this combination of difficult and stupid a lot—it works with any kind of audience. But there were single persons—real jazz enthusiasts—who looked at me distrustfully. In  those years Tommy Dorsey was my model at the trombone, plus my crooning and tapping..... To a Charlie Parker fan I was the bride of the Devil. LOL That was long before I changed to trumpet and discovered Aebersold.

When first I met our guitar player he was a Django Reinhardt fan who over the years morphed to a Charlie Parker disciple. When he more and more went over to riffs I felt like there was no bottom anymore and the few bebop titles he added to the program really stressed me. Those were two worlds and his looked like antimatter to me. I had no idea how to comprehend that in my little world. Most people preferred my world to his—I sold better than his bebop scales. I think that was the reason why that swingtett went on for years and it was mainly the stupid tapping. Today I will dance a chaconne anytime and without pay, but you have to throw real money at me to make me tap!

If you play The Song Is You in 434 Hz, you must be pretty much exactly between E and E♭. Speaking with Charpentier that's between quarrelsome and boisterous, and cruel and hard.

MrYikes said
... quarrelsome and boisterous, and cruel and hard ...

Those where Marc-Antoine Charpentier's words and I wonder whether he really believed in them. He socialized with whip-smart people, very critically thinking, science geeks etc.

Handel's friend Johann Mattheson describes similar ideas and doesn't really sound like he's convinced.

Each kind of traditional instrument has certain keys where they sound best, but I don't think this goes for electronic keyboards. I can easily transpose a midi sequence in C major to any other key, it just sounds higher and lower then. But if you violinistically change to 434 Hz it's different: your E♭ will probably sound even softer. I had planned to try Evah Pirazzi for months, now I just read they have a very high  tension and what the consequences are: they are not good at piano and pianissimo, but very loud. That makes sense to me, for you need to involve more bow pressure to make strings with high tension ring. These strings are not good for my kind of music, which is also mostly supposed to ring out gently.

MrYikes said
...Our sax man was constantly on the guitarist because of his voicing, saying there was no bottom in it, giving him only two or three notes.  It sometimes got loud. ...

Hahaha, I guess your sax man came from traditional jazz and would probably have been happier with a traditional rhythm guitar with four beats in  each bar. Which your guitarist probably found primitive and dull. I was not that opinionated because I did see his point. I was just not steady enough in keeping time to deal with it, like all musicians who come from dixieland jazz and 30s swing style. I learned it years later by working with Aebersold play-alongs, where I had to deal with riffs all the time.

I like the sound of open strings and changing positions is a no-no. Which certainly is an ancient music thing. Romantic ideas about the violin tone are different and there keys with lots of ♭♭♭♭♭ are just naturally. People differ in their ideas and likings because they prefer different styles. Personally I'm not a fan of the A♭ on the D string. If I can avoid it I like the sound better. 

MrYikes said

How do you do that?  Maybe I'm misunderstanding.

I love the Bb on A string(Stormy Weather) but playing open A can catch me off tone (My Way) so I use 4th finger, but I do use open A once in a while just to check myself.  

My major keys are G, C, F, B; my minor keys are e, a, d, g—there are lots of opportunities to involve open strings. How am I doing that? When I began to teach myself the violin, last year in May, I considered open string notes the guideline of my fingering. Whenever something sounded wrong, I corrected my fingering. I had tuned the open strings of my violin, so these notes kinda are the law and I have to obey that—pathetically spoken. In classical singing I was taught the note before the note, so this was not new to me. The open string sounds false if the fingering of the note before it was inaccurate. I'm very strict in this point and maybe my students would soon run away if I was a violin teacher.

I think the open notes of the G, D and A string aren't a big drama—the open E obviously has always been in classical music. I heard several times, there is something going on like open-E-phobia and there were musical directors who would prohibit it because it might be dazzling. Plus, it can be a technical challenge if you play a fast phrase up to that E. My opinion is, if I train myself on involving that open E into my phrasing, I will learn to master it. To me there is no E on the A string, it's strictly prohibited and I consider it laziness! Well, that's again pathos, but I find open Es extremely nice, so why wouldn't I change to the E string? This certainly is the esthetics of the baroque era which aimed up towards the light. The romantic esthetics go down to earth and rather prefers the dark. When time begins in music, the menuet dancer goes up in the air, whereas the waltz dancer of the romantic era goes down. You can also see the upwards tendency in baroque fashion. I can search my ancient music CD albums for hours, it is very difficult to find an E♭ major piece there. I don't dare to say none, but it must be pretty much none.

I heard about change of positions pretty late, in fall last year, when I had already performed twice in our club. I was downright scared when I read about it on YouTube. But then I watched the videos of professional baroque violin players, who never change position—with one exemption: One violin player went very high on the E string and therefore changed to another position. I've seen dozens of videos and they all tell me, "Take it easy baby, you don't have to!"  But of course, if I watch professional players who play Brahms, Schubert or whatever, they change positions all the time and on all four strings. My guess is, that these people avoid open strings, because their sounds differ too much compared to sounds on high positions. That's why baroque technique sounds different, even if played on a modern violin.

 Violin is a very interesting instrument—that instrument is teaching me amazing things I had no idea about before!!

No, this is no baby talk to me. Its normal violin talk and okay.

Move my index finger on the G sting to note A? Not necessary, for this is his official job on the G string. When my fingerboard hand moves to the G string, the index finger knows "A is my place and I'm not allowed to move anywhere else, unless there's an harmonical transition." Harmonical transitions are the exemption, my index finger will then stretch or shift out half a note higher or lower. Take for example the following chord progression:

|?♭ ⁴/₄  F | Fm| C | .....

The key is F major, I start with an F major chord—that means my index finger is automatically on note A where he normally has to stay all the time. He will rest on postition A or he just hovers over there, always ready to go down to his home postition A. Progressing from F major to C major means basically no change, but here is a transition through F minor. And that means indeed, index finger shifting to note A♭. You could consider this changing position, but my index finger has order to go home when Fm is over. To me it's a harmonical shift and no general change of position. Note A keeps being home position of index finger. Anything else would confuse my system.

There could be other harmonical transition like:

|?♭ ⁴/₄  F | E | Am| .....

The third of E major is note A♭, which tells my index finger to move half a note higher until E major is over. On A minor he's probably needed more than before, so he has to go home anyway.

This would of course cause my index finger to move down to note F♯:

|?♭ ⁴/₄  F | D | Gm| .....

The third of D major is note F♯, but on G minor there is no such note, for note A is the sixth of G minor and my index finger knows that.

The reason why I follow that rule is, I would never have learned to improvise to chord symbols or by ear, if all my fingers hadn't their firm place on each string. Like the hammers of the piano: every hammer has its string and none of them will shift to a neighboring string. Which sounds like an awfully stupid system, but my brain work are the rules of chords, scales and composition, so there's no time for counting my fingers, which always have to know their place. I tried to improvise in F minor, the relative minor of A♭ major, but this is confusing my whole system right now. There are too many shifts away from the home positions of my fingers, so I get lost. On the ♭-side of the clock of keys I go no further than B major and G minor right now. In the future I will be able to learn the total harmonical shift also for E♭ major key and C minor key, but certainly not 2016 for I have a concert of two hours in December and I'm not gonna confuse myself with stuff I will not need in my December concert. The repertoire of my program is already perfect and ready, there are pieces in G minor in it, but not even B major. My violin will play a few melodic themes, but mostly I will have to improvise.

I'm not saying, there are no E♭ chords in my program. My favorite air by Johann Christian Bach is in G minor key and there is an E♭ chord in there:

CIACONA (air over a harmonical chaconne loop)

|?♭♭ ³/₄  Gm |  D  |  E♭ | D4 D D :||

But of course, if I would play pieces in E♭ key or its relative C minor, there would be more shifts to chords like A♭ major, C minor, F minor, B minor etc. and I would get lost.

So,,keep doing what you're doing until the concert.  When I'm working out notes for a new song, I have to use the keyboard, the violin is just to messy to keep everything clear in my head.

But for anyone else reading this thread, at least try what I wrote so that you can see that the fingering stays the same for all major scales.  Then go back doing what you've been doing, just tuck that info in the back of your head.  It's all about making sense and clarity of the fingerboard.