module music(clk, speaker);
input clk;
output speaker;

reg [27:0] tone;
always @(posedge clk) tone <= tone+1;

wire [6:0] fastsweep = (tone[22] ? tone[21:15] : ~tone[21:15]);
wire [6:0] slowsweep = (tone[25] ? tone[24:18] : ~tone[24:18]);
wire [14:0] clkdivider = {2'b01, (tone[27] ? slowsweep : fastsweep), 6'b000000};

reg [14:0] counter;
always @(posedge clk) if(counter==0) counter <= clkdivider; else counter <= counter-1;

reg speaker;
always @(posedge clk) if(counter==0) speaker <= ~speaker;

endmodule