If you convert a click track to a MIDI signal on a master track, can you then use that to speed up/slow down the audio in Cubase, without changing the pitch. Thanks.
Charlie, hi.
The short answer to that is no, though many terms are used in your question. So I’ll cover a couple of topics here.
A click track usually implies a metronome giving a “click” on beats 1,2,3 and 4. This is to help keep the musicians in time and to avoid a song speeding up, or even worse, slowing down. A click track is often output from an audio sequencer, the tone is usually a Cow Bell sound as this can cut through pretty well in the headphones (lots of mid).
As you mentioned conversion and master tracks, you could be talking about a time code that has been recorded onto one of the tracks of a multi-track tape machine, this is in fact simply an audio signal, if you listen to it, it sounds rather like a modem signal - nonsense to our ears. However, the audio signal has a great deal of meaning to the equipment in a typical studio, once converted into electrical form, much like a modem.
The audio signal is usually generated from a unit that has the sole purpose of outputting a time code. The most typical format for time code is the SMPTE standard, (originated from the film industry). SMPTE time code is a studio reference clock if you like, it is calibrated in terms of hours – minutes – seconds - frames. So 01,03,54,24 equates to 1 hour, 3 minutes, 54 seconds and 24 frames. SMPTE can utilise a variety of frame rate standards, though a studio must operate at the same frame rate throughout, i.e. all equipment in the chain needs to have the same frame rate selected. The clever part is that a studio uses this reference clock to enable all of a studio’s equipment to be synchronised.
The SMPTE generator generates the time code and also converts it into an audio signal, which is then recorded onto a tape track (we go and get a coffee while this is taking place). Once the tape channel has the code recorded onto it we no longer need to feed the SMPTE code into the tape machine. However, on playback the generator listens to the tape machine’s output (on our SMPTE track) and converts this audio signal into Midi Time Code (MTC).
Using a sequencer such a cubase we can then send this MTC into the MIDI IN socket, and if cubase is set to “synch” we can start a cubase sequence running. Any good quality sequencer will be able to “lock” to this SMPTE code (called MTC in the MIDI world). One of the machines becomes a master and one is slave. Typically the computer running the sequencer is designated the master so by pressing play on it the tape machine comes to life and chases the sequencer. i.e. 16 bars into the middle of a song will have an absolute reference point in terms of SMPTE. Therefore, so will the recorded audio on the tape machine.
Used in this configuration the tempo cannot be altered because the audio on the tape will become non-synchronised. You must set the tempo carefully before the session. Speeding a tape machine up will naturally raise the pitch of the audio.
If a digital system is used for the MIDI and the audio recording the same problems exists. MIDI information can be tempo changed very easily. i.e. if you think your MIDI sequence is too slow simply change the tempo and it all plays faster. This is because MIDI does not record real sounds. MIDI information is only a set of instructions which then plays sound modules, or VST instruments etc. i.e. when you record a note on a keyboard with a MIDI sequencer you are saying you want to record a certain pitch and at a certain velocity (loudness) for a certain length of time. No sound information is recorded, merely an instruction. We can then play that instruction back and we hear a sound. i.e. the instruction is set to play a VST instrument etc. We can change the VST instrument easily and hear a bass drum or a flute! Tempo changes are simple because the sound module just plays the instruction set faster, or slower.
Recorded audio is very different, regardless of analogue or digital. Here the actual sound IS recorded, that is to say, the sound is captured and converted into electronic form and stored. So the audio running alongside our MIDI sequence is in fact “real”. It IS the sound although converted into a different format. There is no clock embedded with this recorded audio, there is no instruction set for playing sound modules, therefore it can not be sped up or slowed down with a MIDI master track tempo change. You can digitally process a tempo change on the individual audio segments (very easy in Nuendo) but you cannot simply alter the global tempo and have the audio stay locked with the MIDI.
The implications of all of this are that it really is best to get the tempo “spot on” before you start recording, or importing any audio samples. Having to change the tempo (and all of the audio) at a latter stage can be troublesome.
Recycle is one such application, which has tried to address this problem. Recycle works by slicing rhythmic audio samples up into individual audio hits. These individual hits can then be triggered and can follow tempo changes in MIDI sequence. Personally, I’m not a convert of this method as slicing parts up creates havoc with room reverbs and sample ambience. i.e. you can end up with a very unnatural sounding sample. Though very good for certain techniques, if you want to use the individual slices for the creation of a totally new riff.
Hope that helps
Chrish
