ColorMusic is a cool application for Mac OS 9 that lets you “play” an image my moving your cursor across it, converting the colors at each point into the pitch, velocity and duration of MIDI notes.  The site that used to host it is no longer in service, but as it has a license that allows for free distribution, I have created a mirror download for the program here.

Note that as this is an OS9 application, you will need to set up an emulator environment such as SheepShaver to be able to run it.

Colormusic – .sit file with application and readme

ColorMusic_11_OS9 (.zip w/ readme)

ColorMusic AppOnly (uncompressed .tar containing app file only)

The text from the readme is included below.  Please note that the contact and download information that it includes no longer works, so to get the application you will need to use the direct link on this page.   I do not have a copy of the source code, so the download contains only the application and the readme.

ColorMusic 1.1
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What is ColorMusic?
ColorMusic plays sounds with QuickTime software synthesizer, by converting a color to the pitch, velocity, duration of a note. You can also save your play as SMF (Standard MIDI File).

System Requirements
System7 or later
QuickTime,QuickTimeMusicalInstrument2.5 or later

Quick Start
1.Select “Open…” from “File” menu. It is good to open DesktopPicture you usually use.
2.Move the cursor on the image.
3.Sound will be created from the color under the pointer. White circles indicate you which pixel is playing.

Option setting
Choose “Option” from “File” menu.

*Pitch,Velocity,Duration
You can assign Pitch,Velocity,Duration of the note to RGB(Red,Green,Blue),Lightness,Hue,Saturation.
[Pitch]
60 is middle C. You can set from 0(low) to 127(high).
[Velocity]
You can set from 0(silent) to 127(loud).
[Duration]
You can set from 1 to 1000ticks (1tick=1/60second).

*Frequency to pick color
If you like faster tempo, set this value small.

*Instrument
You can choose the instrument.

Scale setting
If you select any scale except “None”, the pitch of the note will be changed to the inside of the scale.

ShowStatus
You can see Pitch,Velocity,Duration of sound at the upper left of the window.
Chose “ShowStatus” from File menu to set this function on/off.

Hints
If you stop the cursor,sound is off.
Sound is off if you push shift or capslock key.
This software runs under background.
If sounds delay, please quit other applications.
Max Polyphony is 64 notes.

Freeware
You can freely use, distribute this software.

Contact Author
Shinichiro Hirama: hiramas@alles.or.jp
WebPage: http://www.alles.or.jp/~hiramas/English/
You can download Source code from this page.