A chord transposer is a reference or software application that transposes, or converts, chords in one musical key to another musical key. Using a simple chord transposer chart means transposing chords one at a time, whereas a software application may be able to transpose an entire piece of music. There are also in-between solutions, such as chord wheels. For musicians who cannot transpose on the fly, a chord transposer can be a simple solution to changing the key of a song to suit a performer, such as a vocalist who requires a specific range.
A simple chord transposer chart is a grid, showing rows going across horizontally and columns descending vertically. Looking across the top row, one sees the 12 keys listed, and descending the columns are the chords of each scale. To change from one key to another using such a chord transposer, one must merely locate on the left the key the music is written in, then refer to the column of the key one wants to rewrite the chords for and find the replacement chord in that particular key. By performing this process at each instance of a chord in each particular music sheet, one can find the replacements for all the chords in that particular song.
A chord transposer wheel can be found in any music store that sells guitar accessories. It is possible, however, to make one using card stock to cut out two wheels, one wheel being smaller and superimposed on the other. A hole punched in the middle will allow the smaller wheel to spin around over the larger wheel. The outer wheel lists all of the 12 keys of chord scales and the inner wheel has the same 12 keys. By referring to the outer wheel, one can find the original key, and aligning this to the desired key beneath it, allows all of the chords for that particular scale to be seen in their order for transposition of all the chords in the song.
For computer users, there are software-based chord transposers, which let a user input the key of a piece of music and the key to which he or she wants to transpose. Depending on the software, a user may have to transpose a piece one chord at a time or all at once. Some software is local, meaning the user installs it on his or her computer, and some is online, so the user can simply navigate to a website.
On the simple chord transposer grid chart and chord wheel, the 12 keys are divided between major, minor and diminished chords. These are the three categories of chord key scales. It is necessary to match to a Cmaj if a song is written in Cmaj, as matching a transposition to a Cmin or Cdim would not yield the correct transposition chords. Noting the major, minor, and diminished designations on the sheet music is necessary for correct adjustment with a chord transposer.