The sort of software that is used for this sort of thing is commonly called a DAW - Digital audio workstation. It's a broad name for this categoryof software because their functionalities and capabilities encompass just about everything audio-related that you can think of. The overwhelming majority of songs and albums are recorded utilizing DAW's nowadays.
There are many different DAW's made by lots of different companies - Logic, GarageBand, Live, FL Studio, Reaper, Pro Tools, Sonar, Cubase(which is the one I use), and more. All of them are good for what you're mentioning, Habibilove. You can record your own vocals(or any instrument), and easily re-arrange it, re-record, edit, mix, and process it to sound however you want.
All these programs may also utilize VSTi's (virtual studio technology instruments), which can be given instructions (via MIDI - musical instrument digital interface) to play whatever you want. There are additional elements to VSTi's that can make their sound very expressive, and sometimes come close to sounding like real instruments(with a lot of practice). Although, it will never be able to sound quite as good as a human player. Nevertheless, it's great for making placeholders, so that you can show instrumentalists what you'd like to be played. Something to bare in mind, though: songs don't have to sound 'organic' to sound good.
I think there may be some sort of
online DAW coming along, but it's not quite there yet. It's still possible to share elements of your compositions, either by sharing the MIDI files, or by sending discreet recordings of your various song elements(vocals only, guitar only, piano only, etc), commonly called stems. If you have the same DAW as another person, the entire project can be shared.
Seriously folks, if any of you are interested in doing more with your music ideas, this is something you should try out.