How can I create a "bouncing ball" (sing-a-long style) effect using Final Cut Pro X/Motion5?

Here's a basic approach: http://sight-creations.com/fxexchange/sc_ftbball.zip

This Title is 5 seconds long by default. If you need longer for a single lyric line, then you'll need to rework the template in Motion. The timing is set by a Build In Mandatory so you can *shorten* the Title and maintain timing across variously timed copies (time stretching to longer than 5 seconds is not recommended - break lyric lines into smaller chunks if you don't want to modify it in Motion.)

Suggested workflow:

Type in the lyric line. Add dashes between sung syllables, etc. Try to evenly space out syllables (you can refine spacings later - I recommend using Kerning and/or Tracking when possible.)

Establish the bounce rate with the Bounce Speed parameter. (it helps to loop the title playback) and match as closely as possible the beat.

Use the OnScreen Control to position the start ( the bouncing ball starts at the TOP of a peak preceeding the downbeat on the first syllable) -- This will assist you in lining up the bouncing ball to the text.

Set the playhead near the end of the title -- by default, the bouncing ball path is shown -- you can use the "peaks" to space the lyrics but mainly you'll be matching where the ball hits the beat. Use the Horizontal Move Rate to provide the progress across the screen (also helps match the typed lyric syllables to the beat of the bouncing ball. [You will easily see what I mean when you make adjustments.])

TURN OFF the Show Bounce Path option.

Once you get the first line down, Option-drag copies (this is keep from having to set the bounce speed and travel rate for every line) and simply change the lyric text and the starting position.

The remaining parameters:

HMR Offset (Horizontal Move Rate offset) will stop the horizontal progress of the bouncing ball. The ball will continue to bounce in place at that point, unless:

Opacity Timer is set. You can adjust this parameter to have the ball "disappear" at the end of a line. You'll have to experiment with it a little. A value of 0 will not turn off the ball at any point. Higher values will start to shorten the length of time the ball is visible. The weird thing about it is, if you set it "too short", it will flash off for a time and turn back on. Trim the title at that point to hide its return.

Bounce Height: you can adjust how high the ball bounces.

Start Position: normally, you would position the ball path with the OnScreen Control, but you can use the X position manually to keep the vertical alignment across your title copies.

Top line shows the OSC and increased bounce height -- lower line shows the bounce path active.

HTH!