Dundee United: Siegrist, Smith, Reynolds, Edwards, Robson, Butcher, Bolton, Pawlett, Harkes, Clark, Shankland.

Substitutes: Deniz, Sporle, Powers, McMullan, King, Fotheringham, Appere, Neilson, Fuchs.

Ross County: Doohan, Randall, Iacovitti, Donaldson, Reid , , , Charles-Cook, Kelly, Vigurs, Lakin, Mckay, Stewart.

Substitutes: Tremarco, Gardyne, Shaw, O'Connor, Grivosti, Hylton, Tillson, Paton, Laidlaw.

Livingston: Stryjek, Serrano, Brown, Guthrie, Devlin, Bartley, Holt, Pittman, Mullin, Sibbald, Emmanuel-Thomas.

Substitutes: McCrorie, Ambrose, Taylor-Sinclair, Fitzwater, Lawson, Forrest, Robinson, Poplatnik, Tiffoney.

Motherwell: Chapman, O'Donnell, Gallagher, McGinley, Maguire, Campbell, O'Hara, Polworth, Watt, Lang, Cole.

Substitutes: Archer, White, Hastie, Devine, Cornelius, Johnston, Hussain, McDonald, Long.

For now, we will turn our attention to league business and, with a reduced card in the top-flight, four teams all have the chance to leapfrog Kilmarnock into fifth place.

Dundee United and visitors Ross County sit in sixth and seventh place, respectively one and two points behind the Ayrshire side.

Livingston and Motherwell, who meet in West Lothian, are three points off Kilmarnock but would need unlikely handsome wins to overtake them on goal difference considering the hosts are nine goals worse off, while their visitors would need a four-goal victory.

Image source, BBC Sport

The 2019-20 Scottish Cup - remember that? It is another one of those competitions in the "finished in the season after they started" category as a result of the Covid-19 pandemic.

At 16 months by the time of its proposed Hampden Park finale on 20 December, it will go down as the longest-ever Scottish Cup to be played to a conclusion.

The semi-finals at long last take place this weekend, both at the national stadium, with Hearts facing city rivals Hibs today and Aberdeen taking on holders Celtic tomorrow.

Give yourself something to do before kick-off at Hampden by clicking the link below to remind yourself of what happened before the virus held the competition's drama in suspended animation.

Scottish Cup 2019-20: Story so far

Sportsound is just just starting on BBC Radio Scotland MW.

Joining host Richard Gordon are former Dundee United striker Jon Daly, who is at Tannadice to watch his former team take on Ross County, while former Livingston manager Allan Preston watches their game with Motherwell.

Later at Hampden, Liam McLeod and former Scotland striker Billy Dodds are the TV commentary team, while on radio Alasdair Lamont will be providing commentary ably assisted by former Celtic goalkeeper Pat Bonner and ex-Aberdeen defender Willie Miller.

Click the links above to listen and watch.

Welcome to another busy day of Scottish football. It climaxes with the long-awaited Edinburgh derby in last season's, yes, last season's Scottish Cup semi-finals.

Heart of Midlothian and Hibernian kick-off at Hampden Park at 17:00, but before then we have an aperitif of two games in the Premiership and an almost full card in the Championship, League One and League Two.

Stay with us for the build-up, live commentary and post-match reaction here on the BBC Sport website and on BBC Radio Scotland.