well at 46 be prepared to play a lot of mana song.

1. offensive songs like chants will be resisted a TON of the time.
2. speedup combat buffs will generally be handled by the enchanters or occasionally
the shamen. if your raid does not have at least one enchanter i would recommend
eliding that raid.
3. you will be totally ineffective at charming or mezzing plane mobs

so given all these things, what are you left with? if you happen to end up in a tank group
(you will almost never be put in the pull group due to bard song random aggro bugs) then
you could play level 1 song and heal and damage shield if you really wanted to, but i would
suggest parking yourself next to the cleric and singing mana song while swinging weapons.
if you are in a caster group then there is not much point to singing anything but mana song,
heh.

one note: turn all songs off on the pull. and don't start any song until you are damn sure
the enchanter has any extras mezzed, or else you will be one dead bard very quick. follow
the directions of the raid leader to the letter. and don't be one of those hyper players who
seem unable to sit still. the last thing you need is to aggro something through a wall when
your spellcasters are low on mana.

ok one more note: since you are playing a limited selection of songs, you generally will have
a couple slots open. one good song to put in there is our bind sight song. bind sight to the puller
and you get a nice tour of the zone and you get to see what's going on.