First you have to define "bad song." A non-hit? A song un-related to the plot?
Sometimes I see comments that indicate the writers do not understand the function of songs in a score and the placement of the songs in terms of pacing.
Someone complained about the song "Little Lamb" in GYPSY and thinks it should have been cut. He could not be more wrong. In fact, Jerome Robbins tried to cut the song but Jule Styne rightly insisted it be kept. While true it doesn't really advance the plot, it does help explain Louise's unhappy situation..ignored at her own birthday party, and unsure of her true age it is touching moment and without the song her character would lose much of its initial arc.
Even more important is its role in the pacing of the show. At this point in Act One we have had a lively (and noisy) Overture, a brief kiddie routine, Rose's introductory number "Some People" (with a lot of screaming leading into it and in the middle of it), a number of argument scenes, some noisy kiddie/vaudeville numbers and Ethel Merman blaring her way through 3 songs. We need that short quiet moment to reflect. If you took that song out the first act would become relentless. You may not like the song for personal reasons, but its role is very important to the success of GYPSY. I happen to think it has a lovely, plaintive melody and appreciate it. I think GYPSY is score without a single bad song barring, of course the purposely awful vaudeville bits which are more humorous than irritating.)
Other scores that I feel lack a single "bad" song: ANNIE GET YOUR GUN, BABES IN ARMS, BRIGADOON, CAMELOT, CAROUSEL, COMPANY, FINIAN'S RAINBOW, HELLO DOLLY!, THE KING AND I, MAME, MERRILY WE ROLL ALONG, OKLAHOMA!, NO STRINGS, NO NO NANETTE, OF THEE I SING, PETER PAN, SHOW BOAT, RAGTIME, SAIL AWAY, HIGH SPIRITS and SOUND OF MUSIC. (These are all scores I return to again and again, yet never tire of and never skip a track.)
Cast albums are NOT "soundtracks."
Live theatre does not use a "soundtrack." If it did, it wouldn't be live theatre!
I host a weekly one-hour radio program featuring cast album selections as well as songs by cabaret, jazz and theatre artists. The program, FRONT ROW CENTRE is heard Sundays 9 to 10 am and also Saturdays from 8 to 9 am (eastern times) on www.proudfm.com