This version of City Piano light uses one single sample that is a concatenation of all separate samples. In the instrument json file every note id (i.e. a note name or a note number) maps to an array that contains the position and the duration of the original sample in the concatenated sample. Like so:
20: [0, 500],
21: [500, 650],
22: [1150, 450],
Theoretically, this version should load faster because instead of 88, only one http connection needs to be made. In practice however, it is a bit slower. This is probably because the conversion from mp3 to PCM data is slower with larger files.