Mazurka
Invention
Fugue - this would fit nicely - more difficult than concerto!
Passacaglia
Toccata
Prelude
sarabande
arabesque
Also, while it is possible <or was> to "chorus" together vocally, doing the same instrumentally still eludes.
Chamber music - playing with someone else - might add a degree of difficulty - then you could add:
duets
trios
quartets
quintets
and the whole bard guild playing together - symphony!!!!
<<If I can't cast thunderclap, you can't summon the dark lord of the abyss to devour the flesh of the innocent>>
