for(int j = 0; j < n_of_drums; j++)
			{
				DDUMP(query[DRUM]);
				dlgSelectDrums.lengthList.Set(i, AsString(query[DRUM]), ( AsString(query[METER]) + "m - N: " + AsString(k+1) + " of " + AsString(n_of_drums)));

pardon my ignorance (and laziness to check the zip with full source), but is it ok the for has "j" and the Set takes "i" in first parameter?

Also when the key is "AsString(query[DRUM])", you may produce string like "i,query[DRUM]" for keys, and then extract the query[DRUM] by splitting the key with ',', if you insist to have that data encoded in key. Just an option, I would probably consider in PHP (where the thing is slow as hell already anyway, and writing str manipulation is easy too)... but in U++ I think having a vector with query[DRUM] values around and using pure "i" (or j?) is easier to write, read and maintain...