Fans went crazy on Monday (28 July) after queuing up for hours to catch a glimpse of the teenage duo at one of their tour signings at HMV in Bristol.
Charlie Lenehan, 15, and Leondre Devries, 13, released 'Hopeful' via Simon Cowell's Syco label this week, and the anti-bullying song sold out within minutes of the store opening.
There was such a frenzy, that management had to draft in extra security.
HMV's Senior Events Manager Simon Winter said: "We've not seen anything like this for some time. We had 5 Seconds Of Summer earlier in the year and thought that was pretty crazy but this is just incredible.
"There are hundreds of fans lining the streets," he continued. "They've turned up from all over the country, some have even travelled from France to catch a glimpse of the boys!"
With CDs flying off the shelves, Sony Music are now rush manufacturing more copies to produce enough for the remaining dates of the signing tour this week.
In fact, it probably comes as no surprise that BAM are currently battling it out for the top spot on this weekend's UK music chart. Midweek chart results show the talented duo are sitting at number two, just behind Canadian band Magic! with their single 'Rude'.
It seems music mogul Simon is rather proud too. He tweeted yesterday (29 July): "Bars and Melody number 2 in the charts after one day. That's a result."
'Hopeful' by Bars and Melody is out now. The single also features brand new track, 'Shining Star', which was co-written by BAM themselves.
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Watch BAM's video for 'Hopeful' below: