This tool will display a note for two beats and play the note on beat three. You should read the note on beat 1, sing the note on beat 2, and hear in beat 3 what the correct note is.
Choose a pitch range (as MIDI note values), and a tonic note. Set weights for each scale degree (in solfege), and for each desired interval. Weight 0 means that the given note or interval will not be generated. Weights for notes and intervals are multiplied to choose which note to play next. Additional intervals can be added, any interval beyond those listed effectively has weight 0. If you configure things weirdly, such that it can not choose a next note, it will fall back to playing the configured tonic note.
Each of these tools has a configuration import/export feature to save your configuration (and presets) in JSON, as well as edit them by hand. To import a saved configuration, paste it into the box and use the Import Config button. Press the Export Config button to replace the text in the box with the current configuration. Use Control+A to select all of the text, copy it, and paste it somewhere to save or edit.
This is a companion to the Pitch Match tool and the Chord Match tool.
This tool is free and open source software. Feel free to check out the source code and submit changes at the hosted repository.