Bass players come and they go, they can be replaced without much difference to the band. So can drummers, although when you start changing guitarists or singers things start to go a bit pear shaped. You only have to look at what happened to Aerosmith when Joe Perry stopped playing with them for a while, and Van Halen haven't been the same since David Lee Roth decided to take off.

I really do think Hugh is a very good bassist, and Tico a very good drummer, and they would both be hard to replace, but it can be done without much change in the quality of the music. It may cause arguments within the band, as the guys may not gel as well together, but drummers and bassists, don't tend to write much, they just tend to chip in a little or pick up their tabs (written by others), learn how to play in time, and thus do their job for the band.

Ok now Dave. I think he in Bon Jovi is irreplacable and I think keyboardists have to be creative and find the right melodies for the songs. Dave is a classical piano player who writes his own songs/melodies, as we all know from his solo albums. Therefore I think he is very important when it comes to writing music. As you probably know he co-wrote In These Arms, and that is one of my favourate BJ songs of all time.

In my opinion it is mainly Richie and Jon who write the songs, with a little help from the others. I think Dave will come up with melodies and they'll try to fit the write ones in, or maybe Jon or Richie might say "why not try something like this....". Tico will probably provide the right beat for the song, or he may receive suggestions on what kind of beat to play, and then he can build on it himself, and make it sound better (as all good drummers should be able to do). I think Hugh may get the bass parts written for him by Richie, or he may co-write them with Richie, or maybe even Jon (when he plays rhythm guitar is some songs). I definately think that the guitarist/s and bassist need to be on the same wavelength in order to create the write mix for the song.

On the whole they probably write their songs as a band, buts as I have said Jon and Richie probably do the bulk of the writing and they get Dave, Tico and Hugh to chip in a little.