The .7z extension indicates a compressed archive created using 7-Zip, a free and open-source file archiver.
This is the more famous of the two, known for its somber, march-like opening that transitions into a more agitated middle section. OP55.7z
7z uses the LZMA and LZMA2 algorithms , which generally offer much better compression ratios than the standard ZIP format—often 30–70% better . known for its somber
The 7z format specification is modular and supports extremely large file sizes (up to 16 exbibytes) and Unicode filenames. 2. The Content: Chopin’s Nocturnes, Op. 55 OP55.7z
The "OP55" prefix refers to the two nocturnes composed by Frédéric Chopin between 1842 and 1844. These were dedicated to his pupil and friend, . Nocturne No. 1 in F Minor