I think the point of the passage is a condemnation of complacency. Improvising is not being condemned as such, any more than eating lamb or using lotion are condemned as such. These things, though not wrong in themselves, had become wrong only because the people were using them to distract themselves from what they should have been doing. Today we might say something like, "You sit there in your designer clothes with your iPods in your ears..." Take a look at the passage in context and see if you agree:
Amos 6:1-12
Woe to you who are complacent in Zion,
       and to you who feel secure on Mount Samaria,
       you notable men of the foremost nation,
       to whom the people of Israel come!
2 Go to Calneh and look at it;
       go from there to great Hamath,
       and then go down to Gath in Philistia.
       Are they better off than your two kingdoms?
       Is their land larger than yours?
3 You put off the evil day
       and bring near a reign of terror.
4 You lie on beds inlaid with ivory
       and lounge on your couches.
       You dine on choice lambs
       and fattened calves.
5 You strum away on your harps like David
       and improvise on musical instruments.
6 You drink wine by the bowlful
       and use the finest lotions,
       but you do not grieve over the ruin of Joseph.
7 Therefore you will be among the first to go into exile;
       your feasting and lounging will end.
8 The Sovereign LORD has sworn by himself—the LORD God Almighty declares:
       "I abhor the pride of Jacob
       and detest his fortresses;
       I will deliver up the city
       and everything in it."
9 If ten men are left in one house, they too will die. 10 And if a relative who is to burn the bodies comes to carry them out of the house and asks anyone still hiding there, "Is anyone with you?" and he says, "No," then he will say, "Hush! We must not mention the name of the LORD."
11 For the LORD has given the command,
       and he will smash the great house into pieces
       and the small house into bits.
12 Do horses run on the rocky crags?
       Does one plow there with oxen?
       But you have turned justice into poison
       and the fruit of righteousness into bitterness-
Kent