In Chopin's Nocturne in E-flat Major, Op. 9, No. 2, the technique employed to connect long notes smoothly to each other in the melody is known as legato playing. This technique involves playing the notes in a connected manner, ensuring that there are no gaps or interruptions between them.
Chopin often uses slurs in the notation to indicate which notes should be played legato, and he also employs the use of phrasing to guide the performer in creating a smooth, flowing line. Additionally, the use of pedal can further enhance the legato effect, allowing notes to resonate and overlap, contributing to the overall lyrical quality of the piece. The combination of these techniques results in a beautifully expressive and cohesive melody.