| What I have researched...
Bass players have been tuning their basses to higher pitches ever since someone tried to play solo on one with crappy gut strings. Koussevitzky was I believe the one who popularized the practice of tuning up a step. Anyone who has spent time with gut strings knows that using thinner strings and tuning up a step or more improves the solo projection of the instrument. I have seen a German method book from the turn of the Century which makes referece to all manner of different tunings and states that strings should be selected based on the highest desired tuning arrangement.
It should be pointed out that the comercial gut strings most available today are solo strings ("super solo") and the like with gauges similar to that recommended by Findeisen as ideal for tuning up a step. Jazz and folk players started using the solo strings tuned down for ease of playing, and now you can't get heavy gut strings without special ordering them. Gut strings comomnly used from after Beethoven until around WWI were thicker and more rough than those usually available today. Don't get confused with gut strings in the baroque to mid classical periods when refinement of tone was more important than volume. As a side note, The idea that string tensions went way up when steel strings came around is to some extent bogus. Of course old Italian basses that were originally viol family instruments were not designed to handle the extra tension of steel strings since they were more lightly constructed in some cases, but French , English and German basses from the 1800's should be very capable of handling steel strings provided the overstand will accomodate
lower string height. I've actually seen one Jaquet with a thick top and a tension reducing saddle. Why? The top is thicker than that of my new bass.
The practice of tuning the bass to fit the music partly fell by the wayside when steel strings became the norm since steel strings only work well withing a certain range of tensions. Plain gut strings will work well up to the point that they break which is like an octave above their normal intended pitch. Also with the rise of public music education, more standardization was required to churn out more mediocre orchestral bassists. So now - orchestral and solo is it unless you want to talk about tuning in 5ths.
-Jon | 
