Run existing song software to help you decide what you want your software to do. Pick software whose source code is open source. Source code is the text that developers compile to produce an executable program. Three open source song programs are orDrumbox, UltraStar and AutoLyrix.
Read the documentation that comes with the song software's source code. The documentation will indicate the language that the development team used to write the software.
Compile the song software from its source code by using a free development kit for the language you read about. You can get a free Java development kit from Oracle, and a C kit from Open Watcom or Microsoft. Read your kit's help file for specific instructions on using the compiler.
Run the song software in step mode, using your development kit's debugging tool. This mode lets you execute the software's statements one at a time. Executing programs in this way lets you examine variables and runtime pathways, which helps you understand how software works.
Write down, as you're executing the software in step mode, the value of all variables when the software produces music or sound. Also, write down the names of the functions and their parameters that cause the sound to be heard. Doing this will reveal how the song software works.Once you have detailed notes describing how each sound-related function works, you can change the software. Continue stepping through until you've written these notes.
Write down your ideas for improving the song software. Make your notes as detailed as possible, so you can more easily write the program code to produce these improvements.
Write the program code to implement one of the improvements on the list. For example, if you wrote that the software should play songs at a slower tempo, use the knowledge you gained from stepping through the software in step 4 to write the code that slows the tempo.
Repeat the previous step for each remaining item on your list of improvements. When finished, you have created your own song software.