OK, I've had a look at tiBc?.kas file formatstz81.129.43.181 127 (40 to 7F in hex) are used (in pairs) for the timestamps. The value appears to be incremented five times per second so here is my assupmtion:

00:00:00.0 = "@@", decimal {64,64}, hex {0x40,0x40}

00:00:00.2 = "@A", decimal {64,65}, hex {0x40,0x41}

00:00:00.4 = "@B", decimal {64,66}, hex {0x40,0x42}

00:00:00.6 = "@C", decimal {64,67}, hex {0x40,0x43}

00:00:00.8 = "@D", decimal {64,68}, hex {0x40,0x44}

00:00:01.0 = "@E", decimal {64,69}, hex {0x40,0x45}

00:00:11.0 = "@w", decimal {64,119}, hex {0x40,0x77}

00:00:12.6 = "@<DEL>", decimal {64,127}, hex {0x40,0x7F}

00:00:12.8 = "A@", decimal {65,64}, hex {0x41,0x40}

00:00:13.0 = "AA", decimal {65,65}, hex {0x41,0x41}

00:00:30.0 = "BV", decimal {66,86}, hex {0x42,0x56}

00:01:00.0 = "Dl", decimal {68,108}, hex {0x44,0x6C}

00:10:00.0 = "nx", decimal {110,120}, hex {0x6E,0x78}

etc... (where <DEL> represents the 'Delete' keystroke).

This seems to allow for about 20 minutes of karaoke, which is probably more than enough in most cases! Not sure what happens when it gets to {127,127} though. Wraps around?

Sorry if anyone doesn't understand all that