The "Turbo" colour palette in Audio Magic's Make a Spectrogram tool is the
Turbo colormap by Anton Mikhailov at Google LLC.

  Turbo   https://gist.github.com/mikhailov-work/ee72ba4191942acecc03fe6da94fc73f
          Announced 2019 as an improved rainbow colormap for visualization.

Audio Magic does not use any of the original source code. What is used is
the colormap data itself: forty-eight stops sampled evenly from the
published 256-entry sRGB lookup table, interpolated back to 256 entries at
runtime (see src/lib/audio/spectrogram/palettes.ts).

The original carries the SPDX identifier Apache-2.0 and the copyright
notice reproduced below. Apache-2.0 requires that recipients of the work,
or of derivative works, receive a copy of the licence and retain the
copyright notice — which is why this file is served rather than only cited
on the /credits page.

Copyright 2019 Google LLC.
SPDX-License-Identifier: Apache-2.0

The full text of the Apache License, Version 2.0 is available at:

  https://www.apache.org/licenses/LICENSE-2.0

Licensed under the Apache License, Version 2.0 (the "License"); you may
not use this file except in compliance with the License. You may obtain a
copy of the License at the URL above.

Unless required by applicable law or agreed to in writing, software
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WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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under the License.