Am I going to need 2 pianists for this arrangement?

I have never tried arranging a symphony for an ensemble that didn't include woodwinds AND isn't exclusively piano. That is, until now. I started arranging Symphony no. 1 by Mendelssohn(I figured it would probably be the easiest non-Beethovenian symphony to arrange(Gustav Mahler and Johannes Brahms both have a similar symphonic style to that of Beethoven)) as my "Romantic Era Symphony Arrangement Challenge" as I call it. Now I'm wondering, will a Piano sextet be enough? Or am I going to have to increase that to a Piano septet(Piano Duet + String Quintet)? Here is how I'm going about it:

• Strings: Play the original notes as written by the composer for each of the string staves
• Piano: Get the rest of the orchestral sonority across(Woodwinds, Brass, Tympani)

But, I'm finding that I have the high and mid register woodwinds in the right hand and left hand and I already don't have room for any bass notes whatsoever, not even from the bassoon staff(I try to never go past an octave in each hand unless I have to, and if I have to go past an octave in each hand, I never go past a tenth(I mean, how many pianists can play twelfths? It must be a minority of even the advanced pianists that can reach that far. And sustained twelfths are even harder unless you have hands like those of Rachmaninoff.).  The opening of the symphony I am arranging has a homophonic texture and uses all the instruments in the orchestra, so I feel like I absolutely need to include all the woodwind notes(Some, especially in the Flute - Oboe pairing, I am able to collapse from 2 notes into 1), including the bassoon notes. The brass and tympani, I feel don't matter as much here in the opening measures of the first movement as they might later on in the symphony.

But, if I try to include all the clarinet notes on 1 hand along with the flute and oboe notes, it is going to be impossible to play(the flute and oboe alone already make it hard with those almost constant octaves). So, am I going to have to expand the ensemble I am arranging for to a Piano septet(Piano Duet + String Quintet)? Here is a link to the PDF of the symphony I am arranging, so that you can see the notes yourself as written by the composer(First Movement starts on page 5 of the PDF):

http://ks4.imslp.info/files/imglnks/usimg/f/f8/IMSLP214825-SIBLEY1802.18342.401d-39087009398282score.pdf

18 minutes ago, caters said:

I have never tried arranging a symphony for an ensemble that didn't include woodwinds AND isn't exclusively piano. That is, until now. I started arranging Symphony no. 1 by Mendelssohn(I figured it would probably be the easiest non-Beethovenian symphony to arrange(Gustav Mahler and Johannes Brahms both have a similar symphonic style to that of Beethoven)) as my "Romantic Era Symphony Arrangement Challenge" as I call it. Now I'm wondering, will a Piano sextet be enough? Or am I going to have to increase that to a Piano septet(Piano Duet + String Quintet)? Here is how I'm going about it:

• Strings: Play the original notes as written by the composer for each of the string staves
• Piano: Get the rest of the orchestral sonority across(Woodwinds, Brass, Tympani)

I'm concerned about the ideas you have with the instrumentation. Yes, piano sextet can be good, but where strings only play what was written for them in the original piece and the piano only plays woodwinds/brass/timpani? To me that is copying not arranging. It was written by a master composer for orchestra and just casually changing the instruments that play the lines is going to really change (maybe even ruin) the sonority. Remember, the piano is so different from any other orchestral instrument, partly to do with its decay. The greatest composers and arrangers recognised this.

24 minutes ago, caters said:

But, I'm finding that I have the high and mid register woodwinds in the right hand and left hand and I already don't have room for any bass notes whatsoever, not even from the bassoon staff(I try to never go past an octave in each hand unless I have to, and if I have to go past an octave in each hand, I never go past a tenth(I mean, how many pianists can play twelfths? It must be a minority of even the advanced pianists that can reach that far. And sustained twelfths are even harder unless you have hands like those of Rachmaninoff.).  The opening of the symphony I am arranging has a homophonic texture and uses all the instruments in the orchestra, so I feel like I absolutely need to include all the woodwind notes

Do you though? If the strings are playing any of the same notes as the woodwind, you could think about omitting them. There is nobody that said that arrangers have to use every single note that was written by the composers.

26 minutes ago, caters said:

So, am I going to have to expand the ensemble I am arranging for to a Piano septet(Piano Duet + String Quintet)? Here is a link to the PDF of the symphony I am arranging, so that you can see the notes yourself as written by the composer(First Move

Do you think you are going to have to expand the ensemble? This is fast turning into us telling you what to write and you writing it. If you think you should, do it. If you think you shouldn't, don't do it. It's as simple as that. One little piece of advice though: I have learnt from being a pianist in ensembles such as piano trios that the piano easily overpowers the strings. Be careful what you write - especially if you decide to use two pianists.

Do you plan on getting this performed? 

From personal experience coordinating 2 piano players in an ensemble is hell. Do what you want but keep in mind how realistic the logistics are, maybe add another wind instrument rather than another piano. Pieces for 2 piano are almost always difficult to synchronize and often produce unfavorable results (unless you are working with extremely advanced players and have lots of rehearsal time to kill) Also keep in mind the sonorities between 2 pianos will become washed together and it will thus be hard to differentiate each instruments line in say a symphony. In more contemporary pieces it makes sense sometimes to use 2 pianos because typically each piano has a very different timbrel role. Take this with a grain of salt but I personally would stay away from two pianos in a piece like this.

To make arrangements or reductions you don't have to rewrite or "represent" all the instruments or notes.

The important facts for this kind of works:

1. Write the melody (as it is).

2. Write the bass line (as it is).

3. In the middle: supporting harmony, rhythmic figures, countermelodies.

Many times you cannot put everything. If no, how the hell did Liszt to arrange the 9 symphonies by Beethoven for piano solo (and much more symphonic and operatic works)?

Think and arrangement is done for two reasons:

1. To accomodate a piece to a specific set inf instruments you have (band, quartet, small orchestra).

2. To make something quite different (from symphony to piano solo).