Hi: As to your question concerning works with “low clarinets”.
The most beautiful passages in any work with choir and orchestra, and soloists from the 18th century is the Mozart Requiem. This is a work written in the last days of his life and in fact finished by a student of his, but it remains in a very important way the finest work especially when you consider the fact that this is the only large , and celebrated work which features two basset horns and two clarinets as well.
In fact the entire piece begins with a solo for two basset horns right in the middle register of the instrument and if you have not approached this work before, please do check it out, yes, just for the clarinet music alone. After that you can simply get to know it at your own leisure and hear how a composer in his last weeks, can write arguably the most lovely work of the era but perhaps the greatest choral work of all time.
The opening of the work is utterly simple with the two bassets going in somewhat contrary motion, and the other voices forming a canon as they are added. It will stay within your mind for a very long time.
Because it is contrapuntal I always somehow think of it as the signature of Mozart, but that could be my own romantic feeling about this piece.
As far as the deeper sounding clarinets this is the best piece written. At about 53 minutes it is a bit longer than the Requiem of Faure but still shorter than many Masses written at this period of time.
Mozarts relationship to the clarinet is rich historically. He wrote many works for it , many works of chamber music, and of course, the Trio and the Quintet, and the Clarinet Concerto (which of course was written for clarinet bassett, which is not the basset horn) but an instrument invented by Anton Stadler purportedly a friend and debtor of Mozart who played the Concerto on the instrument. The clarinet bassett fell out of use after that and the concerto is now played in a somewhat edited version because the original went down to low c on the clarinet bassett.
And recently performances have been made on special clarinets with a low c attachment making the part playable without the octave transpositions.
But of course, all considerations are out on this piece for it is perhaps the most beautifully made Concerto fo the entire period, that is to say, the form is perfect, the harmony and conterpoint varied and enjoyable beyond most, yet simple and transparent.
It is for your information the work which is asked initially for any clarinet position in any orchestra. It is that revealing as are many of Mozarts works, butnone like the Concerto
It is even more amazing that unlike Beethoven, Mozart made no sketches or revisions, he just seems to have been a vessel placed by a supreme being, a vessel filled with a beautiful bounty, and when it was finished,when he had completed this huge output, Mozart died. —–