Fair comment on the programme to be broadcast on 22nd, Modette, I've just checked my playlist for the one on Thursday 25th and as far as lead singer/musician goes in that programme the balance is 11 male to 12 female.
I ought to point out that around 80% of the CDs in my collection are therefore the ones that I can choose from - Rocket FM has a disc library totalling zero - are ones that come from unsolicited review copies either from record companies or magazines or the artists themselves. I would reckon that the overall numbers of lead performers in these albums are male.
I wonder if there are figures for the gender ratio figures of albums released by major/independent/specialist labels and whether the proportion is different for each genre (Female hip-hoppers would not seem to be very plentiful - just an impression). I also wonder if the ratio has changed with the years.