Green’s Dictionary of Slang

cat melodeon adj.

[? cat adj. (1) + the supposed tendency of accordion (melodeon) players to fluff their notes; ? or the howling of a cat on heat]

appalling, disastrous.

[Ire]Mayo News 29 Sept. 12/2: [headline] ‘Cat Melodeon’ traffic chaos.
[Ire]Irish Times 4 May n.p.: Carson even attempts to find a history for the greatest expression in Hiberno-English, namely cat melodeon [BS].
[Ire]Irish Examiner (Cork) 29 July 36: And what do you get? A train service which is cat melodeon. ‘We’re getting there,’ is the message from our rail body but what do the punters do while this torturous journev is in progress?
posting at www.boards.ie 21 Jan. 🌐 It’s [i.e. cat = bad] short for ‘cat melodeon’, a reference to a cacophony reminiscent of a feline in heat combined with a badly-played squeezebox, and applied to all things of an equally unpleasant nature.
[Ire]Southern Star (Cork) 16 Apr. 1/7: Kinsale farmer Broadband service is ‘cat melodeon’.