Sit at the piano with the singer standing close enough to the piano to place one hand on the piano. Have the singer close her eyes. Play one note on the piano loudly and ask them to listen and feel the vibration in their hand and arm. Play the note again.
Play a second note several steps higher, or lower than the first the first. Ask her to listen and tell you if the note is higher or lower than the first. Play the first note again, only if she requests it.
Continue with this exercise up and down the scale until the singer is getting the answer correct consistently. Repeat the exercise with notes closer and closer together, until you are playing notes side by side on the piano.
Warm up with the exercise from the first session, with the singer's eyes closed and one hand on the piano. Repeat as needed until he gets three correct answers in a row.
Play each note, starting with middle C and ask the singer to match the pitch. Try each note twice, then move on to the next. Find a note the singer can match, which typically happens the first time; play a three-note scale, starting from that note. (For example, C, E, G.) Ask the singer to sing each tone in succession, going higher, then starting at the top and coming down.
Shift from the first note to the second and start a new three-tone scale, continue moving up, or down the keyboard playing and singing three-note scales.
Start with the exercise from the first session, then do several three-tone scales until his voice is warmed up and he is showing some consistency. Encourage him with each correct note, overlooking the mistakes and focusing on what success there is.
Play and sing five-tone scales, starting with the note your singer first matched. Let him sing with you.
Find a simple song with no more than a one-octave range, and which starts with the note the singer first matched in your last session. Teach only the first two to four measures of the melody to the singer. Send a recording of that melody home with him to practice. That recording should be played one note at a time on the piano.
Continue adding to the song, until he is singing the melody fairly consistently. Choose a new song and practice both in each session. Start normal training from this point.