Quoted from Doot77:
You need to finish the songs to get the 2X, 3X, 5X etc multipliers going. I believe you have to finish 2 songs to get 2x, 3rd song 3x etc. I personally changed the settings to light 2x after the first song completion and find it much more fun and easier to get also.
There is a difference o. The multiplier. The song one gets assigned to one shot like SM arrow completion. After completing 2 songs (default) it is a playfield multiplier. Both end when you drain..