Q I have recently woken my old Moog Prodigy from years of hibernation in a quest to seek out new drum sounds. The problem is, I am very limited without a noise generator. I remember in the distant past hearing that noise could be fitted into the 'old' circuits, and since the men from Moog have long gone I am turning to your magazine for help and information. Is there any chance of fitting a generator, and if there is, where and how can I get one?

Also, talking about Moogs, can anyone tell me about the Moog 55 as featured on Mr JM Jarre's Zoolook album?
David Hunt
London

A First things first; a noise generator can be fitted to practically any analogue synth which doesn't have one. Where a synth like the Prodigy is concerned, what you really have to consider is the value of this synth in relation to the cost of having such a generator installed. The Synth Service Centre ((Contact Details)) reckons that the charge would be around £50-£60 - they'll have to take a look before giving a more accurate quote.

As for the Moog 55, a swift call to Tony Wride at Exclusively Analogue provided the answer. The Moog Modular Series originally comprised six models, each using the 901 series of oscillators: 1C, 2C, 3C, 1P, 2P and 3P - where 'C' stands for cabinet and 'P' for portable. The series was later upgraded to include the 15, 35 and 55 models - each of which used the newer 921 series of oscillators which were more stable and made possible the use of frequency modulation. The number of oscillators in these synths is 3, 5 and 9, respectively, and the 55 invariably included a sequencer. Date of manufacture? Early 1970s, and the 55 was quite a hefty cabinet system.

Q I have worked with sequencers on the Atari ST for some years now but have recently changed to a Mac IIvi with a Mark Of The Unicorn MIDI Time Piece MIDI interface. What I now wish to do is to convert all of my songs over to the Mac where I'm running Cubase v1.8.3.

I've been using the Apple File Exchange to format MS-DOS disks - having discovered that the Mac can't read ST-formatted disks - and to save my songs as MIDI Files on the ST. On running these files through Apple File Exchange in its 'default' mode, I find that the file appears on the desktop but as a grey rectangle which Cubase won't recognise as a MIDI File. What am I doing wrong?
Jim Kirby
Aberdeen

A What you're doing is perfectly correct. The Mac's Apple File Exchange will not recognise a disk formatted on the ST but will allow you to format an MS-DOS disk which the ST will recognise.

The problem is in the different way that the Mac treats files. Both the ST and the PC use a three letter extension to show the file type with '.MID' being used to display the fact that a file is a MIDI File. The Mac uses two different parameters; file type and file creator. The file type for a MIDI File is 'Midi', while the file creator depends on the Mac program on which the file originates; Steinberg Cubase is 'stCU'. Double-clicking on a file launches the originating program by checking the file creator.

It is necessary to set the file type and creator before a Mac sequencer will recognise the MIDI File. 'Resedit' is a standard Mac program that allows you to edit many file characteristics, but I'd recommend getting hold of a shareware program called 'Filetyper' which will let you edit both the file type and file creator very quickly.

Two other options. First, have you been using Cubase on the ST? If so, simply save your song to the MS-DOS formatted disk as an arrangement, use Apple File Exchange to transfer it to the Mac and load it as you would a Mac arrangement. Steinberg, intelligently, kept the structure of arrangements the same across all of the platforms it supports. Second, do yourself a favour and buy DOS Mounter which allows you to read an ST-formatted disk directly into the Mac. It will also automatically set the file type and creator according to the three letter extension - it may cost about £60 but it's well worth it!

Q I use a Roland Sound Canvas SC-155 live and often need to be able to have more than one part playing percussion because of the way that the songs are originally recorded. Being a GS sound module, Part 10 on MIDI channel 10 is always used for the main drum kit, but it would be useful to be able to set another part to a drum kit via MIDI. Can this be done? I've tried changing part 11 to the second drum kit according to the System Exclusive info at the back of the manual, but keep getting 'Checksum Error' on the Sound Canvas's display. What does this mean?
Colin Ward
Gillingham

A Sound Canvas and its derivatives allow a part on any MIDI channel (except for 10) to be set to 'Norm', 'Drum1' or 'Drum2'. The inclusion of two drum parts is so that you can change the drum kit for several parts at the same time but still have access to the drums from two kits - for instance, acoustic and electronic kits. The parameter that has to be altered is referred to as 'Use for Rhythm Part' in the SysEx table. The basic message is as follows (in hexadecimal):

F0 41 UU 42 12 40 1n 15 VV CS F7

...where 'UU' is the Unit number (usually $10), 'VV' is 0 for Norm, 1 for Drum1 and 2 for Drum2, and 'CS' is the checksum (more about this in a moment) and 'n' is the part number. 1 - 9 refers to parts 1 - 9, 0 is part 10 and A - F are parts 11 - 16. Take the example of setting part 11 to Drum2. The message for this would be:

FO 41 10 42 12 40 1A 15 02 0F F7

Where does the checksum of $0F come from? Ignoring the first five header bytes and the final $F7 (end of exclusive), the sum of the remainder must add up to $80 (or a multiple of it). The sum of $40, $1A, $15 and $02 is $71. Consequently the checksum must be $80 minus $71 - which is $0F. This means that any changes to the parameter value must be reflected by a similar change in the checksum. Get this wrong and the Sound Canvas screen comes up with the 'Checksum Error' message you mentioned.