yeahh.. ive been told so many times that my singing is flat and they keep telling me to put in some air. lol! i still don't really understand. weird but i'm only singing "do re me" now to listening to my pitching properly. bahhh. i dunno. a little confused here. some help might be great. i need someone professional now alright!
one thing that constitutes to monotone singing is singing with very little mouth/lip movement. things like "mumble-singing", or not opening your mouth big enough (er... donno how to explain)
try dropping your jaw all the way, to the most relaxed and lowered position you can manage.. when you sing, does your mouth open within that perimeter or hardly open?
if the monotone sound comes from lack of feel, there's not much i can give tips on except that you need to feel the notes..
one habit i teach on developing feel is to improvise on melodies according to your own style.. it doesn't only encourage feel but works on your confidence..
which is another factor that gives monotone vocals.. not enough confidence to sing it out..
if ppl say you have to put in more air, i assume they think it's not loud enough as well?
if you're practicing do re mi, try exercising your lips and mouth with each vowel...
do - your lips should be unpursed and oval or at least round
try "ohhh" first, then add the consonent for "do"
re - semi open mouth, somewhere between a full jawdrop
try saying "airr", that should be the position of the mouth before adding the consonent
mi - when saying mi, do -not- tighten the ends of your lips. loosen your lips
... then sing your own style you don't have to be perfect in speech to sing, you just need to find another way to -use- it and implement it as your unique style..
listen to bjork. she can't pronounce certain consonents clear but she uses it into a personal style that is completely unique that no one can imitate..
some vocalists have lisps also, and they can still sing because they develop a style of using less lip movement and more mouth pallet resonances...
it's all practice and lots of listening..
don't give up..
start by breathing through your diaphragm... then go to the piano and start singing la to a pitch.
and do an octave for a week... u should not sound nasal. because u are doing pop singing, try to put your music infront. the sound should be much more 'front' then 'back'.
you should not sound nasal... if not you are doing it wrongly... once you find yourself straining, do not stress your shoulders. put 3 fingers in your mouth, smile and stress your eyebrows, this will help you pitc better and reach the higher notes.