Fester's half right (which is half more than he usually is) it's generally dead especially in the winter. But the local music scene has grown immensely over the past couple of years. As you said the Great Orme brewery gigs are fantastic, on that note try the Slateman festival in May and Gorjys Secrets festival in July organised by the same people. What shows have you been to at Great Orme Brewery? There's a good chance the same artists will be at the festivals.
Also try Wild Horse Brewery who are starting a new open mic night this month.
Conwy Folk club have a weekly open mic night which is of a really good calibre and very well attended - and also have guest artists every month or so. Most of the guest artists are big in the national folk scene such as the Changing Rooms, Greg Russel, Ange Hardy who all played last year.
Venue Cymru have a few gigs in the arena every year but there should be a lot more - also check out the next level events and Phabstock which is in August on the promenade.
Fountains I believe also have an indie rock night about once a month and you can regularly see local bands in Cooneys and Club 147. Bodafan farm and Penrhyn Old hall are also known to run ad hoc gigs as does the Labour Club in Junction. Junction also hosts the annual busking festival which is really good and doesn't get enough press. Oh the Kings Head on the Orme also does an Annual music festival outside called Headstock which is always packed.
