I play the strings (violin/viola) and keyboard (piano) and I was a keen musician at school and university where I participated in numerous musical activities. My main interest in western classical music has been the transition from the ornate tradition of Baroque Music (and to some extent late Medieval Music) to the brief yet volatile interlude of the Classical Period, which contains some very interesting artistic innovations within a relatively short span of time. Below are some of my favourite pieces from this era (and beyond):
Brandenburg Concerto No. 3, G-major
J. S. Bach's Brandenburg Concerti are absolutely magnificent. No. 1 aside, I love all of them, especially No. 3 since, as a strings player, No. 3 has an amazing orchestral structure and some unique melodies and harmonies that only Bach is capable of. The last movement of No. 3 is especially impressive, since it has a three-by-three parallel structure between the violins, violas and cellos which permeates throughout the movement. The main melodies are also based on two motifs, namely ascending/descending scales with a slight modification of the main theme in the famous first movement and an ascending arpeggic sequence, both of which complement each other in this layered contrapuncto.
Bach Violin Concerto No. 2, E-major
By far the grandest violin concerto yet written, Bach's second violin concerto in E-major is a masterpiece. Bach composed three attested violin concerti (all transcribed for the harpsichord too), and the second one is the most special of all since it is the first violin concerto which has a big orchestral counterpart to the violin soloist. It is also significantly longer than the other two (judging by its length it may well have been the longest violin concerto yet written) with a proto-sonata form structure in the first movement and a proto-variations form in the last. Typically Bach, it is mathematical in melodic and harmonic structure, and the melodies of this concerto are just sublime. The first movement is just beautiful while the second is the most melancholic piece of Baroque Music I have ever heard. I played this piece in my youth. I would like to play it again.
Mozart Symphony No. 40, G-major
Whenever people ask me to explain the classical sonata form and symphonic structure, I always play them Mozart's famous Symphony No. 40, which is not only an all-time masterpiece but also the best structured piece of music I have ever heard. The first and last movements are the best examples of sonata form in history, since they are perfectly executed from the composer's point of view. The second movement (Andante) is also a classic slow interlude which typifies slow movements in the classical era, and the third movement is the best Trio and Minuett I have ever heard. All in all Symphony No. 40 is a landmark in western classical music with its magnificent structure and classic melodies. Mozart at its best, and his best comes in several shapes, sizes and forms and there are quite a few more masterpieces of his that stand right up there with this one.
Mozart Sinfonia Concertante, E-flat-major
As a violin/viola player, I have a sentimental attachment to violin/viola duets, for which there is a surprisingly rich repertoire. Some people say that Handel-Halvorsen's Passacaglia is the best, and that is an amazing piece, but my personal favourite violin/viola duet has to be Mozart's revolutionary Sinfonia Concertante, which is just unique in western music. A slightly modified sonata form which accommodates both the violin and viola soloists, its harmonic progression is extremely clever (like Brandenburg three above).
Beethoven Symphony No. 7,
Ludwig van Beethoven was an innovator in every sense of the world, since his music very much expanded conventional musical forms and brought new boundaries to people's musical imagination. One of his most underrated pieces in this regard is his seventh symphony, which contains some unprecedented orchestral structures.
Sibelius Violin Concerto
I have had numerous conversations with fellow violinists what the best violin concerto is of all time. We always mention the classics, like Mendelssohn, Beethoven, Tchaikovsky, Brahms, Elgar. However, it is surprisingly how many times I have ended in agreement with fellow violinists that Sibelius Violin Concerto is not only one of the best but the very best violin concerto in history, since it really is the most amazing piece of violin music that I have ever heard. Three unique movements of symphonic scale: the first one is dramatic, deeply melodic and contrapunctal, and virtuosic from the violin soloist. It is truly amazing as it is structured like a piece of drama with instrumental correspondences like dialogues. The second movement is just sweet and beautiful with one of the most moving melodies of all time and a cheesy orchestral accompaniment which lies on a par with some of the best romantic symphonies. The last movement is just amazing with the most virtuosic displays in violin history. I cannot say how much I love this piece.