Many of us are familiar with Carolan's melodies. But what if I told you that he might not recognise many of the melodies now attributed to him? And that the complicated style in which they are now usually performed – with tricky bass lines and full chords – are not at all how he is likely to have played them? The most reliable written sources – transcriptions made from live performance by old Irish harpers in the 1790s – which would get us closer to the real Carolan, have generally been ignored. Modern editions and recordings usually take much later, reworked versions of the tunes, transcribed from fiddles and flutes, or even Victorian piano arrangements, as their starting point. In this illustrated videoed talk, I outline these long-standing problems; I introduce you to the most significant – but neglected – Carolan sources from the 1700s, and I outline my recent discoveries about Carolan’s likely performance idiom, including my new hypothesis about what his lower hand played.