Download and install one of Zero-G's or PowerFX's Vocaloid 2 singing synthesizers in your digital audio workstation. These vocal synthesizers use Yamaha's Vocaloid technology to simulate both male and female singing voices. To make digital vocals with a Vocaloid singer, type in the phonemes that you want the voice to sing, then use MIDI notes to program the melody. To save time when creating digital vocals, combine phonemes into words using the Vocaloid User Word Registration table, then use these words in your song.
Use Virsyn's Cantor software instrument to make digital vocals. Cantor is a true synthesizer, as it generates all of the vocal sounds that it makes, rather than employing recorded samples. This allows Cantor to produce exaggerated vocal styles in addition to the typical male and female voice simulations. Use the piano roll interface in Cantor to enter notes, then type the desired syllable above each note. Cantor automatically converts the syllables that you enter into phonemes. Set the voice's character using the instrument's parameters section.
Install the free Syng2 singing synthesizer plug-in from Xoxos.net. Syng2 uses two MIDI channels to create digital vocals. The first MIDI channel controls the melody, while the second determines which phonemes the synthesizer produces. The plug-in includes a phoneme chart to illustrate which MIDI notes activate which phonemes. You can also use the synthesizer's Words section to construct entire words out of phonemes, then trigger these words using a third MIDI channel. Playing these pre-constructed words is useful for live performances, as you can set up the vocals ahead of time, rather than putting them together on the fly.