It is a sound of 6 seconds containing a single note of music: si (493. 9 hz) with a amplitude of 1. The sound is sawtooth. Work on the envelope ( the curve) reduced to regular intervals on the first 2 seconds then there is 2 seconds without modifications before the last 2 seconds where there is regular intervals again. This sound like morse.
This is a MIDI rendered Ludwig van Beethoven's Symphony No. 9, Movement 2. It was created from a public domain MIDI file (https://commons.wikimedia.org/wiki/File:Sym_9_Second_Movement.mid) with LMMS using a public domain RKHive Unison soundfont (http://rkhive.com/banks.html). I just made minor adjustments like adding effects for better sound. I release this under CC0.