Optional Skill Hack for The Red Concordant:

Anyone can attempt anything. Base roll is roll under, but not equal to, stat with disadvantage.

If this seems harsh, remember that many older games had a house rule of rolling a 1 on a d6. That is a 16.67% chance of success. This is about the same as rolling under a stat of 9 with disadvantage.

As characters advance, they can gain a specific skill. As they improve, the character evolves from disadvantage, to +2 to the die roll, no adjustment to the die roll, add 1 to the primary stat when rolling, add 2 to the stat when rolling, to rolling with advantage.

This give you six steps of advancement from totally unskilled (roll with disadvantage) to a master (roll with advanatage). The choice of six steps was deliberate as there are six steps of DC in 5e D&D.

As far as what specific skills are available, there are suggestions based on existing class abilities (like Delicate Tasks), but skills are largely determined by players. The Referee determines the primary Stat used and the player records it on the character sheet under that stat. Taking a skill promotes the character from unskilled (roll with disadvantage) to novice (add 2 to die roll).

If a player wants Ultimate Mandolin Solo as a skill, so be it. I would call the primary stat Charisma, but YMMV.

The progression with titles:
Unskilled Roll with Disadvantage
Apprentice Add 2 to die roll
Novice No modifier
Journeyman Add 1 to the associated stat
Expert Add 2 to the associated stat
Master Roll with Advantage

The titles serve as a way to talk about relative skill level more naturally, just like Close, Nearby, Far Away, and Distant are ways to talk about distances more naturally.