This file is from Wikimedia Commons and may be used by other projects.
The description on its file description page there is shown below.
Summary
DescriptionSpectrogram of Bach's Chorales for Organ.jpg
sonogram (spectral view) of a fragment of one of Bach's Chorales for Organ. The pattern the harmonics create is simply beautiful, this music is not just to be heard but also looked at
to share – to copy, distribute and transmit the work
to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.