Cannot read/play files written by writemidi

[grinsted]

The midi files i write appear to be malformed(?). Example

addpath c:\miditoolbox

halftonespan=24;
root=64;
bpm=120;
duration=1/8;

Y=rand(10,1);
Y=round(Y*halftonespan)+root;

nmat=zeros(length(Y),7);
nmat(:,1)=(0:length(Y)-1)*duration;
nmat(:,2)=duration;
nmat(:,3)=1;
nmat(:,4)=Y;
nmat(:,5)=100;
nmat(:,6)=nmat(:,1)*(60/bpm);
nmat(:,7)=nmat(:,2)*(60/bpm);

writemidi(nmat,'test.mid',120,bpm);