The Trio des anches was apparently intended to include three movements, but there is no trace of a first movement. The fragmentary last movement was later finished by Roussel's friend, the Belgian composer Arthur Hoeree, but this version is rarely played.

The second movement, however, was the last music that Roussel finished before his death. It is interesting that he worked on the slow second movement first because in so many works of his mature period the slow movement is the heart of the entire work; apparently it held this prominent position during the composition process, also.

Although the Andante is finished to the point of being playable, several details remained incomplete. For example, there are no dynamic or phrase markings, and it is possible Roussel may have changed even the name of the piece; for this Andante is marked, curiously, adagio.

Just what kind of music did Roussel conceive immediately prior to his death? His slow movements are of two general types: either filled with anguish and a sense of railing futilely against Fate (as in the string quartet or Third trio), or calm and contemplative (as in the Serenade or Concert pour petit orchestre). The Andante from the Trio des anches falls squarely into the latter category. It is highly contrapuntal and seemingly all of one piece; there are few divisions into internal sections. The music simply flows, continually, making few concessions to the listener.

It was the composer's express wish that this piece not be performed publicly. Its premiere, then, was a private performance in Paris.

Full of delicacy, the idiom of this andante is amazing; the style of Roussel evolved constantly and always unexpectedly until this very end. [??]

More severe than the corresponding movement of the String Trio, it gives no indication of a decline in creative energy. [Basil Deane]