Sing Along is the replay version. Melody is the add-a-ball version. Playfields are the same. Sing Along is spotlighted; minor scoring and rules differences are detailed at the end of this guide.
Collect a few numbers of any colour, then repeatedly collect them all for points by shooting at the white saucer. Completing 1-2-3-4 of a single colour lights that saucer occasionally for Special on Sing Along, or extra ball + reset the colour on Melody.
Awards 5 points and the 1 of the corresponding colour (white, red, yellow, green, from left to right). The red lane lights the red bumpers for 10 points and the yellow lane does the same for the yellow bumpers. Lighting red and yellow bumpers also light the left and right slingshots for 10 points each, respectively.
Between the top two bumpers is a swinging gate that can be traversed from either direction that scores 50 points.
Between the bottom two bumpers is a bullseye standup target that scores 100 points.
Upper side lanes: white and red on the left, yellow and green on the right. 100 points each.
Red and yellow are at the top near the bumpers; white and green are standup targets near the bottom of the playfield. 100 points each.
White 4 is on the left out lane, green 4 is on the right out lane, red and yellow 4 are split center drain lanes in the middle. Use the center post between these to keep the ball in play when possible, and be mindful of draining under the flippers in that case.
There are no in lanes, the slings meet up with the flippers directly. This game has shorter 2 inch flippers as opposed to modern 3 inch ones. Slingshots score 1 point, or are lit for 10 points when the red or yellow bumpers are lit.
There are 4: white, red, yellow, green, in order. Each saucer scores 10 points, plus an additional 10 for each number of that colour that is lit, then shoots the ball to the saucer on its right. The green saucer sends the ball to the right flipper. Ideally, a bunch of numbers are collected across all colours, then shoot the white saucer to get credit for all of them.
When all 4 numbers of one colour have been hit, the corresponding saucer can be light for special. I believe the special can be rotated by any 1 or 10 point switch other than the saucers themselves.
Pop bumpers: the bumpers are lit by the 100 point center target, not the red and yellow top lanes. Going through the 50 point gate unlights the bumpers. The red and yellow top lanes do still light the slingshots, though.
Number scoring: 1s, 2s, 3s, and 4s give 50, 50, 50, 100 points respectively on Melody, instead of 5, 100, 100, and 5.
Lit saucers: When all 4 numbers of a colour are lit, that saucer is solidly lit for an extra ball. Collecting that extra ball unlights that saucer's numbers, and they must be collected again. If playing Melody but the extra balls are disabled, try to only get 3 numbers of each colour so that the saucer value stays high and doesn't reset.