Sight Singing is the ability to sing music by sight, rather than imitating what you hear. So far you have only sang minor melodies that used Do through Fa. In the next few exercise you will be singing melodies that ascend up to So and le. If you have been following the recommended order of exercises, you have already played, dictated and identified these melodies, so they should be somewhat familiar to you.
To review how to sing Do through Fa in natural minor go to How to Sing in Minor.
Below is an example of how the solfeg syllables apply to the C minor scale.
If you use the solfeg system regularly, you will become accustomed to the "feel" of each note in the scale.
Remember that three of the syllables are different from what we used in major. These syllables are changed to remind you that they are a ½ step lower than the same scale degrees in major.
Be careful that you sing Me, and Le a half-step lower than you would for the major scale. This will create a half-step between Re and Me, and between So and Le. The fifth scale degree, So, is the same as it was in major.