A transpose program is software that changes music from one key or pitch to another. Depending on the type of software used, the music can be entered manually or it can be entered through a keyboard attached to the computer. Some transpose programs even allow users to compose music directly in the application and transpose it into a variety of keys for different instruments and voice pitches. There are programs available that can transpose simple melodies, chords and entire scores.
Music written for one instrument will almost never sound correct when played by an instrument in a different key. A B-flat clarinet, for instance, needs music written for a B-flat instrument. The music itself can be in any key, but it must be arranged for the particular instrument. A middle C played on the piano will not have the same pitch as the same note played by an instrument that is in another key.
For example, a B-flat clarinet used to play that note will sound a full step down from C, so transposition would be necessary to make the notes sound the same. A transpose program can take such a melody and automatically lower each note by a full step. Once that is done, the piano and the clarinet could each be used to be play the same melody, and the notes would sound the same, even though they are a full step apart on the musical score.
Many musicians have the ability to look at a piece of music written for a different instrument key and transpose as they play. They mentally calculate how many steps higher or lower the new notes need to be. Skilled and experienced musicians may even be able to take a piece of music they have never seen before and start playing in a different key.
A melody written for someone singing in a tenor voice may be too high for someone who sings in a baritone, so musical transposition can be used to lower the pitch of the tune in this case as well. Some vocalists can easily transpose to a lower or higher key as they sing. Any vocal music can be transposed up or down in the same way instrumental music can. Often, a song can be transposed into several keys so an entire band or orchestra can play it together. Another common reason to use a transpose program is to change music from a difficult key to one that is easier to play.
The transposition tools found in a transpose program can determine whether the program is easy or difficult to use. Some of the most common methods of inputting music are by typing in the notes according to musical notation, or choosing notes with the mouse. A transpose program that allows input from a keyboard will probably be faster and easier to use because the music can simply be keyed into the program. This type of software should allow the music to be transposed into any key, making it suitable for a variety of instruments and voice ranges.