George's father Edward Onslow quit Parliament after only one term amid a sex scandal that forced him to emigrate to France. While in France Edward married and had four children. George Onslow was the oldest son and was born in 1784. The family had a good life in France until the French Revolution of 1789 when Thomas Onslow was jailed on account of his nationality and was eventually exiled from France in 1797. George joined his father as they toured Europe to provide young George with an education. They ended up back in London where George continued his to study the piano as well as history, art, horsemanship and other subjects befitting a young gentleman. He also learned to play the cello and spent time with friends playing the quartets of Mozart and Haydn.
Despite his piano studies, he never gave a public recital nor did he consider becoming a composer. It was an overture to a opera of Méhul that inspired him to try his hand at composition. His first attempt was a set of three string quintets that were published and became popular. Through the encouragement of friends and his publisher, he got serious about composing and took composition lessons from Anton Reicha, French composer and teacher. Although Onslow wrote 4 symphonies and works in other forms, he specialized in chamber works at a time in France where opera was the most popular form of music. He wrote 36 string quartets and 34 string quintets that were highly regarded in his lifetime. Beethoven, Schubert, Schumann and Mendelssohn all placed him at the forefront of instrumental composers, and it was in Germany where his fame was the greatest and where he was called The French Beethoven.
He had an international career, but remained loyal to France and lived most of his life there. He became a gentleman farmer that owned and ran a castle and was a good businessman in dealing with music publishers. Onslow's works sold very well and he profited by the competition among music publishers to obtain his newest works. For the most part he led a quiet and productive life. He died in 1853.
The String Quartet No. 25 was composed in 1836 and is in 4 movements:
I. Allegro moderato - The first theme is heard straight away and makes its way to a section that has a few sudden outbursts. The second theme has the cello playing a motive as a violin scampers after it. After a short transition to material related to the first theme the exposition is repeated. The development transitions into an exploration of the first theme mainly by modulations to keys that are close to the B-flat home key. The recapitulation repeats the first theme with added transitional material so the second theme segues into the home key. A short coda adds a moderate amount of dash until the movement ends quietly.
II. Scherzo: Vivace assai - The scherzo begins with a run that starts on B-flat and ends on a long G-flat, after which the music skips along in the home key with the phrase ending with three B-flat quarter notes one after the other descending in three octaves. The opening phrase is repeated but this time doesn't come to rest on G-flat but continues to scamper until the first section of the scherzo comes to rest on a high F. This first section has 20 measures in it, with the first eight measures making up two phrases. By phrase extension the other twelve measures give a a feeling of inequality to the first section that is reminiscent of Beethoven. The first section is repeated. The second section of the scherzo expands and modulates previously heard material until the opening run is heard and the section ends in the tonic. The second section is also repeated. The trio begins with an introduction, after which the time signature of the music turns from two flats to three as rapid pairs of identical notes are played as an accompaniment while the first violin plays a slightly halting theme. This section is repeated, after which the trio continues and material is expanded. Much of this section is played pianissimo which gives a rather eerie mood to it. After the trio the scherzo and trio are repeated, this time straight through without the repetition of sections. A short coda ends the movement in B-flat major.
III. Andante grazioso - The slow movement is marked con simplecezza, with simplicity, which suits the gentle tune that is in F major. It proceeds to gracefully unwind at a steady pace until it reaches a minor climax. The accompaniment becomes slightly more complex as the tune continues on its gentle way until it grows more quiet and ends pianissimo in F major.
IV. Finale: Allegro vivace - The finale begins fortissimo with the instruments spitting out a fragment that returns throughout the movement. A second theme theme contrasts, the music bustles its way with the fragment reappearing in different keys and dynamics, but always maintaining a certain harshness, and the movement ends in the home key of B-flat major.