For the purposes of my Capstone, I consider two aspects of music in games:
The musical nature of the gameplay itself.
The musical nature of the control mechanism.
As far as gameplay is concerned, there are three main ways that music is utilized:
The object of the game is to match a desired piece of music.
The game allows for freeform music experimentation.
The game has traditional gameplay that is synchronized with or affects the background music.
Of these types, only the first and second are commonly used in conjunction with a musical control mechanism. Examples of the first are such fabled classics as Guitar Hero and Synthesia, the latter of which is not so fabled, but does make use of the MIDI protocol.
Games of the second type include the DS game Electroplankton, which uses the touchscreen to interact with several "levels" to create music, and the terrible but exemplary Wii Music, which employs the WiiMote as one of a variety of imaginary instruments.
The aim of my Capstone is to use such a control device to create a game of the third type. In this way the music that is input to the game becomes itself the background music, and must meaningfully match the effects in the game world that it produces.
Lo! As one might suspect, there have been almost no games utilizing instruments as control mechanisms where the object of the game is not simply to play music. As it stands, the only game I know of to use such a mechanism is Donkey Kong Jungle Beat. Research has also turned up an intriguing article which I cannot access.
The game will feature one or more levels satisfying each of the below constraints:
In order to succeed, the input sequence must match a second sequence K(j) so that for any j, |I(j).time - K(j).time| < ϵ, where ϵ is chosen to be some arbitrary specificity.
The desired input sequence is independent of time, but consists of several subsequences which are themselves dependent on time. Any disparity between the desired sequence and the input sequence will not result in failure.
Success is entirely independent of time. There are many (or infinite) input sequences that result in success, and as such there is no sequence that results in failure.
Other Unusual "As Different As Chalk From Cheese" Input Devices: