spettro (music player with logarithmic spectrum display)

Most spectrographic music players use a linear frequency axis,
which dedicates the top half of the display to the top octave
(11025Hz-22050Hz at CD-quality), the next quarter of the screen to the
penultimate octave and so on, leaving all the musically interesting
information crushed into the bottom few rows of the graphic.

Spettro has a logarithmic frequency axis, which allocates the same
amount of space to each octave.

It can play most audio files (WAV, OGG, FLAC, MP3, M4A and even the
soundtrack of videos) and shows a scrolling spectrogram of it with
a vertical green one-pixel-wide line half way across the window to
show the current playing position. It has the standard features you'd
expect from a graphical music player, plus a few unique ones of its
own.

Unlike most spectrograph visualizers, spettro is actually useful for
analying music. See the man page, particularly the -a, -g, and -k
options.