- HUM
- Drone
- Ho follower
- Motor's sound
- Sound from a kazoo
- Relative to 10-Down, Jackson 5 song in which the lyrics explain that it has no lyrics
- Running sound
- Be busily active
- Chug along smoothly
- Play a kazoo
- Buzz
- Run smoothly
- Unwanted speaker sound
- White noise component
- Sound engineer's problem
- Audiophile's bugaboo
- Make a number wordless
- Generate wordless notes
- Whir
- Be at a loss for words?
- Sound system noise
- Sing without words
- Busy state of activity
- Drum intro?
- Purr
- Rattle and ___ (U2 album)
- Smooth engine sound
- Run smoothly, as a machine
- Carry a tune without words
- Low monotonous noise
- Play the kazoo
- U2 album Rattle & ___
- Annoy someone in the next cubicle, probably
- Belt with a lid on it?
- Indulge an earworm
- Sing sans words
- Busy sound
- Droning sound
- Forget the words, perhaps
- Speaker interference
- Bustle
- Karaoke singer's filler
- Sound system problem
- Substitute for forgotten words
- Hive sound
- Sing, in a way
- Sing with one's mouth shut
- Fridge sound
- Sign of smooth operation
- Run well
- White noise, perhaps
- Rattle and __: U2 album
- Engine room noise
- Air-conditioning sound
- Fan noise
- Go smoothly
- Sing with a closed mouth
- Smooth machinery sound
- Fire on all cylinders
- Be busy
- Forgo the lyrics
- Seethe with activity
- Motor sound
- Sing with closed mouth
- Sing wordlessly
- Closed-lips sound
- Engine noise
- Make a kazoo buzz
- Engine sound
- Indistinct murmur
- Sing with lips closed
- Sound of a fan
- Low murmur
- How to play the kazoo
- Use kazoos
- Sing with mouth closed
- Vibration sound
- Background noise
- Sing a wordless tune
- What you may get out of your refrigerator
- Sound of an airplane motor.
- An exclamation.
- Bombilate.
- Sing in a certain way.
- Sound of hesitation.
- Be busy: Colloq.
- Ho's partner.
- Sound of activity.
- Sound before drum
- Apiary sound
- Low sound
- Word with drum or bug
- Top sound
- Emulate a bee
- Wordless vocal music
- Low, droning sound
- Proceed smoothly
- Continue without the words
- Continuous sound
- Be busy, as a bee
- Proceed without the words
- Make music on a comb
- Symptom for a car mechanic
- What you can do if you don't know the words
- What fans do
- Accompany musically, maybe
- Run nicely
- Beehive sound
- Good engine sound
- Good noise from an engine
- Vocalize on a kazoo
- Operate smoothly
- Well-tuned engine output
- Bees make it
- Generator's output
- Make music on a kazoo, say
- Run smoothly, as an engine
- What many air conditioners do
- Fake the vocals in Rock Band, say
- Forget the words?
- Sing with closed lips
- Motor noise
- Had smash "Stars"
- Downward Is Heavenward band
- Purr, in a way
- Fail to know the words
- Pass the time, maybe
- Sound like a well-oiled machine
- Sing along without words
- Drum head?
- Forget the lyrics, maybe
- Sound of a well-tuned engine
- Participate without the lyrics
- Dinger or "drum" starter
- Refrigerator sound
- Almost sing
- Drum starter?
- Busy place's buzz
- Good machine sound
- Low drone
- Sing with your mouth closed
- What to do when you don't know the words to a song
- Wordlessly sing
- Ho's follower
- Persistent sound
- Lyricless song
- Forget the words maybe
- Work smoothly
- Sing alternative
- Wordless song
- Prosper
- Electronic noise
- Sound of tires on the highway
- Low, continuous sound
- Drum beginner
- Sing, sort of
- Amp problem
- Choir's background sound
- Copier sound
- Refrigerator noise
- Steady drone
- Run like a well-oiled machine
- What to do when you don't know the words
