Where have all the guitar bands gone?

Take a look at the Top 20 of the Billboard singles and album charts today and you will find that less than 10 per cent of the positions are filled by acts employing the traditional rock guitar-bass- drums-charismatic frontman formula.

This week, rapper Drake, pop singer Rihanna, girl band Fifth Harmony and electronic dance music act The Chainsmokers hold court on the commercial music world's most prominent charts. Barely hanging on as the only bona fide rock bands on the lists are American metalcore sextet Issues and southern rock veterans Mudcrutch.

This has not always been the case.

In the 1950s, rock 'n' roll bands helped kicked off a revolution in youth culture. Rock juggernauts in all their various forms, from The Beatles and Led Zeppelin to AC/DC and Metallica, dominated the mainstream charts and filled arenas around the world in the following decades.

And while these bands still sell music and make the news today, their buying audience is made up mostly of older fans who are unlikely to go out and give the same ardent support to newer and younger acts.

It is telling that pop singers such as Rihanna and Taylor Swift, who both made their debut in the mid-2000s, have sold up to 200 million records and are now in the same league as The Rolling Stones, who have been plying their craft since 1962.

There are only two bands from the 1990s who have gone beyond 70 million in terms of global record sales - the now-defunct grunge icon Nirvana and the still-active Brit quartet Coldplay.

Proclamations that rock 'n' roll as a genre is dead is certainly not new and go as far back as when music icon Elvis Presley was drafted in the United States army back in 1957.

More recently, in 2014, Gene Simmons from Kiss, one of America's most venerated rock bands, created a stir in the music press when he infamously said that "rock is finally dead", telling budding musicians to go audition for The X-Factor, a reality talent show, instead.

The recent edition of pop culture industry event South by Southwest in Austin, Texas, which includes one of the biggest music festivals in the world, had a panel of media and industry players discussing the issue of rock music being sidelined in favour of other genres.

But maybe the question is: Does it really matter that guitar bands employing the rock template are hardly visible on the mainstream pop charts?

There is certainly no lack of new releases from such bands and the past week alone featured fresh music by acts such as American metalcore band Beartooth, indie rock outfit The Strokes and sludge-metal pioneers Melvins.

But these days, pinning any new artist to a single genre is a futile exercise and very few make music that can be described with simplistic terms such as "rock" or "pop".

The homogenisation of genres is a natural result of the evolution of popular music in the last 60 years.

Crossing genres is nothing new, of course.

One of the main reasons why the recently departed music genius Prince is so beloved is that his prodigious output defied easy categorisation. The rhythms can be traced to funk greats such as James Brown, the searing solos take a leaf from rock guitar god Jimi Hendrix's book and the string of Top 10 hits attest to the pop appeal of his hit singles.

You don't have to look far for more examples of cross-pollination in music. The recent spate of new releases from new acts in the home-grown music scene shows the myriad of sounds that influence the new wave of music acts.

Singer-songwriter Gentle Bones, whose concerts at the Esplanade Concert Hall on Friday and Saturday are sold out, straddles electronica, pop and R&B in his new EP, a far cry from his folksy, indie roots.

A recent debut album by rising singer-songwriter bittymacbeth has tunes that will not sound of out of place in a jazz club, indie playlists and Top 40 radio.

Streaming services recognise this blurring of genres as the new normal. When you fire up music streaming service Spotify, you'll find that they use moods such as "chill" or "party" besides the usual genres of pop or rock to categorise music.

Music, whether old or new, has never been so easily available as it is today.

There is just so much music out there that unlike in the past, it's getting harder and harder for any single act to achieve superstar status.

It's likely that fans in the future will focus less on a select group of monolithic stars, whether it's pop acts such as Swift or rock bands such as Coldplay, and spread their devotion to a wider range of music acts.

With so much good music to be discovered, there are fewer reasons to limit your ears to any one genre or act.