musical question

Another daft musical question.

I've been listening to a 1994 CD of the violist Raphael Hillyer playing Bartók, Stravinsky and Shostakovich. The last two are viola pieces: the Elegie and the Sonata for Viola and Piano, respectively. My question is about the Bartók piece, which is his Sonata for Violin solo, arranged for Viola. The question is who made the arangement (no credit on the CD case), who makes these arrangements and in what circumstances, and what's involved in making an arrangement like that.

My first thought was that maybe you would just transpose the piece down a fifth, thus retaining all the fingerings. Not to say that the result would necessarily lend itself to viola technique, but it would be a breeze for the arranger.

Comparing the recording with violin versions, however, I can hear this isn't what happened. The same keys are retained (thus the opening melody still begins with a C followed by a B flat, but in the viola arrangement it is one octave lower). Sounds like it would be quite hard work to re-think all that double-stopping, whose playability Bartók worried over in the first instance with Menuhin, and then not even get a credit for it. I'm constantly amazed by the feats of mathematics and dexterity that classical musicians seem to perform without either effort or recognition.

Perhaps there is a unique person somewhere in the world -  I imagine a stooped, weary-looking but courteous person, always a little distracted - who works in a tiny, slightly musty office in Chicago and whose job title is Professional Arranger of Violin pieces for Viola. Violists call in from all over the world saying "I've always loved [Brahms' Op 78, Mozart's Turkish, Sibelius's first Serenade, etc etc ] do you think I might have it for Friday week?"  Doubtless Ralph Hillyer used the service.

But I'm not sure what I think of the outcome, really. The viola arrangement loses much of the dash and brilliance and ease of the violin version, and those are heavy sacrifices when we're talking about a lengthy piece for solo stringed instrument. It is certainly less instantly attractive, it emphasizes the isolation. Nevetheless a modern ear appreciates some of the added propulsion, e.g. the resonant pizzicati on those thicker strings.

Other things I learnt or re-learnt about violas:

Unlike the violin and cello, the viola is the "wrong" size. It ought to be bigger (20"), but has to make a compromise with the limits of an instrument that can be played under the chin. Only a giant could play a 20" viola. Consequently, there is no standard size of viola. They vary between 15"-18" depending on what players feel comfortable with. 16" is typical. I don't know if this has any relation to the slight sense of strain in the sound (variously characterized as nasal, throaty, attacking, staccato, etc.)- all of these could be ways of registering a comparative thinness of pure tone, hence a higher proportion of scrape.

Viola music is typically scored on the alto clef, centred on Middle C; it is the only really common instrument to use this. (Extended higher-register passages are often scored on the treble clef). In French, but not Spanish, the viola is called the "alto".