i'm gonna explain why playing bass and singing at the same time is very hard: a ~long~ thread (bc i tend to rant & overexplain) to help you appreciate calum hood's skills even more, written by a bassist

bassists who sing live have to keep track of 4 very different and seperate things: the bassline melody, the bassline rhythm, the vocal melody, and the vocal rhythm

when singing, guitarists also technically keep track of 4 things: guitar melody, guitar rhythm, vocal melody, vocal rhythm
however, the guitar melody/rhythm are usually parallel to the vocal melody/rhythm, leaving essentially only 2 things to keep track of.

however, in lead guitar it's a bit different & more difficult than rhythm guitar since the lead guitar might also have it's own guitar riff, but overall both guitars generally follow the vocal rhythm, so singing guitarists keep track of 2-3 things at a time

drums don't have a melody, so singing drummers have 3 things to follow as well: keeping rhythm of the song, vocal melody, and vocal rhythm. however, vocal rhythm follows the drum beat, so these are somewhat parallel, leaving 2-3 things a singing drummer must keep track of.

but the reason we don't see a lot of drummers singing live is because singing requires vocal control, and playing drums requires the whole body to move, making breath control and singing difficult.

all basslines have melody and rhythm, some more melodic, some more rhythmic. example: valentine is rhythmic. she's kinda hot is melodic. os/co is both.
rhythmic basslines are generally harder to sing to. even some very advanced bassists cannot do this, even with lots of practice.

when playing bass, the left hand dictates melody by moving along the fretboard. the right hand dictates rhythm by strumming, picking, plucking, or slapping.

when singing live, calum looks down at the frets as least often as possible because he has to sing into the mic. this means he's had to learn how to play without looking down at his hands and means he can probably play the set with few or no mistakes blindfolded if he tried.

anyways going back to keeping track of things as a singing bassist. it feels like singing a song to the backing track of a different song, except you're also playing the song.

since the brain cannot truly multitask while putting equal attention to both tasks, the bassist must be able to either play the bassline or sing the song with basically no effort. they must be able to ignore the bassline they're playing or what they're singing to do both.

rhythmic basslines like valentine, no shame, wildflower, and youngblood are hard in the sense that a bassist needs to pay attention to the rhythm even more, or the song will sound bad/off. these are difficult to sing to because you need to pay more attention in keeping time.

melodic basslines like she's kinda hot, moving along, and hey everybody are hard to sing to in the sense that you need to be very familiar with the fretboard so that you can sing into the mic w/o looking down to often.

rhythmic and melodic basslines like os/co, teeth, and beside you are the difficult to sing to while playing because of both the reasons for melodic and rhythmic basslines.

i could write a thread miles long on this topic but i'm gonna stop there so it doesn't get ~too~ lengthy (it kinda already is)
the moral of the story is that playing bass and singing is H A R D. so go! go appreciate mr. calum t hood and his talents

end of thread! shoutout to you for reading this whole thing!!
thank you all & love you all xx