ralphw@IUS3.IUS.CS.CMU.EDU (Ralph Hyre) (04/01/88)
[followups to rec.music.synth, where they probably belong] In article <1503@vaxb.calgary.UUCP> radford@calgary.UUCP (Radford Neal) writes >I have a vague recollection back from when I was a first-year student >(1974) of someone demonstrating a program for the PDP-8 that played a quite >good rendition of some piece of music on a radio placed beside the >CPU. In retrospect, this seems moderately unlikely, though not impossible. >If it existed, it must have been some hack... I recall the music lasting >at least 10 seconds, good enough to require 6K samples/second minimum, say >6 bits per sample, doesn't look like it fits in 4K 12-bit words... We're not talking about sampling here! Just a hack for generating musical notes with RFI. Sampling (recording the entire waveform and then playing it back, possibly with some editing) has become 'hot' recently, but it's definitely not the only way of generating music (or speech). You can generate any repetitive waveform (computers happen to be good at square waves) and call it a musical note. The number of repititions per second determines the frequency of the note. Here's a (monophonic) example from the Apple ][ world. (Apple ][ hackers will note that I have used a 65c02 opcodes for brevity.) TONE: LDX #$255 ; Load X register with 255 LDA #$C020 ; click the speaker WAIT: DEX ; decrement the X register BNE WAIT ; Wait some more if the X register isn't 0. JMP TONE ; do the whole thing over again -- - Ralph W. Hyre, Jr. Internet: ralphw@ius2.cs.cmu.edu Phone:(412)268-{2847,3275} CMU-{BUGS,DARK} Amateur Packet Radio: N3FGW@W2XO, or c/o W3VC, CMU Radio Club, Pittsburgh, PA -- - Ralph W. Hyre, Jr. Internet: ralphw@ius2.cs.cmu.edu Phone:(412)268-{2847,3275} CMU-{BUGS,DARK} Amateur Packet Radio: N3FGW@W2XO, or c/o W3VC, CMU Radio Club, Pittsburgh, PA