How much musical instruments can attribute for the success of a song?

Music plays a big role in making a song melodious, a songs tops the list only with good music and if the lyrics are good, nothing like it. But these days we get to hear very few melodious songs, what we hear is all foot tapping music with minimal meaningful lyrics. These songs are an instant hit but soon forgotten too.

That depends on the situation of the song in which, the song has been pictured. A lilting Bhajan needs a serene atmosphere more accent on the lyric and a nominal accent on the instruments. Imagine the same Bhajan with a 200 piece orchestra. This submerges the soul of the song and its nothing but cacophony."Sukh Ke sab saathi, Dukh me Na Koyi" a famous Bhajan from Gopi had minimum instruments.And it was a roaring success
Yes, a song pictured on the hero in a discotheque need more instruments. Otherwise it sounds like a Bhajan sang in a club. Such songs are bound to fall flat.

Music plays a role but according to situation. Sometimes a musician can give the song an altogether different dimension. OP Nayyar famous for use of simple instruments changed the meaning of Film songs with his extra ordinary beautiful rhythmic compositions to the Hindi Films. Even the most ordinary songs composed by him were thundering success.

Instrumental music supplements vocal music. The lyric author, singer and the musician all have a combined role. A song without accompanying music is like food without salt.

In case of new generation songs, it is like must. I don't think people would like to hear today's most of songs without any music. In fact new generation (not all) more enjoys the music instead of singing.. like they can dance in disco just with the music and all that. lol

Music does play an important role in the success of a song but it depends on how much and how long and more importantly, how effectively the instruments are used by the music composer. For example, RD Burman used a myriad number of things in his song including scraping on a plastic comb etc. those songs are still remembered fondly by one and all have not lost their melody even in times of electronic music.

Songs composed now may be an instant hit but are only short lived since the music, even though may sound sweet, lack soul and do not have any heart warming qualities and hence are quickly forgotten! Take kolaveri di song, instant rage and a big hit but such a short life!

It contributes alot.............
Remember mouth organ by Dev Anand Saab in Hai Apna Dil To Awaara

I am a huge fan of music composed by various musical instruments and to me that is very vital for the music to sound good.

It contributes a lot , a good background score is as important as the song itself...I can give so many examples where we remember both the song and the background instrumental score ...Sayonara, Yaad Kiya Dil  ne kaha ho tum, Baar baar dekho to name a few