Hardware based varispeed in Sonar X3

Sonar does not feature software based varispeed like a few other DAW software's do now. 
 
For some purposes a workaround is to varispeed the whole Sonar X3 DAW by offset sample rate.

I could not find too much information if this would work with Sonar (searched the forums and googled).  My goal is
a fast and easy solution to record with slightly offset speed/sample rate by a few percent.  CD players with varispeed can be used to control sample rate offset. This could be the cheapest solution with an old cheap pro CD player.  I borrowed an old Sony CDP-D500 CD player.  This player has varispeed +/-12.5% based on 44.1kHz SPDIF or AES/EBU as outputs.  I tried to sync my Motu 828 mkIII and Presonus Digimax FS to SPDIF from this CD player. MOTU seem to lock with +/- 4.0% and Presonus Digimax FS locked within +/-1.3%.   I think I read that ABBA used 0.5% slower tape speed for recording some of the voices.  I could play and record with offset sample rate.  This will only works on 44.1kHz sample rate.

I also tested a RME Fireface UFX with varispeed yesterday.  I have only tested to do vocals with no dramatic sample rate offsets. I think ABBA used -0.5% tape speed on some of the vocal takes.  I redo each voice in the harmonies several times with  slightly different sample rate offsets  just to make them sound different. Harmonies sounds amazing with this trick.   If the whole mix should be permanently slowed down or increased in speed it would require to use the analog outputs and resample with a different DAW or do digital sample rate conversion.

Samplerate offset in RME can be changed on the fly without restarting Sonar as the driver allows to adjust sample rate offset outside Sonar.  This should be the closest digital version of tape speed as there are no sample rate conversion involved.  I even tried to go crazy with fast variations of the sample rate in playback and it played without pops&clicks (but I don't think its recommended). With Reaper I get a short dropout when changing the SRC based speed.  Sonar could record and play at +/-5% for all sample rates provided by the RME hardware driver.

I'm not sure if all Sonar plugins or software instruments works when the sample rate is offset but  least the few ones I used worked. MIDI drumtrack with Addictive Drums did also change speed as expected.  

RME fireface is not the cheapest solution.  Any RME audio interface with steadyclock is able to do varispeed +/-5% by offset samplerate(slightly less than a semitone). I have seen really cheap used RME hammerfall DSP PCI cards which cost 1/10 of the RME fireface UFX but I wanted a solution which can be used on a laptop with USB port.  
 
I also tried to use RME to clock MOTU 828mkIII and Presonus Digimax FS with their supported sample rates.  It seemed to work with the same +/- 4.0% offset for MOTU and +/-1.3% offset for Presonus Digimax FS.
 
Previously I did export Sonar mixdown to Reaper.  Reaper has no +/-5% speed limit but use sample rate conversion .  I'm not sure if my ears is capable of hearing SRC artifacts for small varispeed offsets.  I had no problem importing the Reaper recordings back in Sonar.    I think it sounded amazing but I prefer to do everything in Sonar and RME let me do just that.
 
Word clocks like Apogee Big Ben can rund with  +/-10% offset but it adds to the cost. 
 
I am not a pro so there might be some disadvantages of sample rate offset which I am not aware of. But for my use it worked great.

I have now done another interessting test for achieving +/-12.5% varispeeds on higher sample rates.
 
I think I read somewhere that a single speed clock can be used to sync generate 2x and 4x speed clocks in the RME.   I had to test this too.  Connected the Sony CD player as master clock for my RME Fireface UFX via AES/EBU input. Now I can slow down 88.2kHz by 12.5% by using the varispeed control of the Sony CDP-D500 CD player.   I have looped a Sonar X3 project with 12.5% reduced speed for half an hour now and it plays without dropouts. 
I also tried to record&play both with 12.5% reduced sample rate and 12.5% increased sample rate and it works.  
The clock from the CD player is probably full of jitter but RME claims to dejitter down to a few nano seconds so I guess its ok.
 
There is a problem increasing the speed from 88.2kHz more than a few %.  At around +4% the RME driver naturally starts to think this is 96kHz audio and switches to 96kHz mode which cause Sonar not starting play or record . The Sonar warning "Device may not support the current projects audio format" is shown.  Then I have to deactivate varispeed and even restart Sonar in some cases.   I do not know how the audio data transfer works but to me it seems like the ASIO audio driver transmits info to the DAW what the normal sample rate is.  I wish there was an option to override that information in ASIO just to fool the DAW software.   Then maybe it even could have been possible to fool the DAW by letting it think its 88.2k while in reality it is 44.1k or 176.4k (+/-1 octave with +/-12.5% varispeed from the CD player).  Maybe there even are simple workarounds for this that I am not aware of.
 
I dicovered a simple work around to let me record/play with 88.2kHz from +4 to +12.5%.   I start record(or play) in Sonar with Sony CDP-D500 varispeed button disabled and then hit the preconfigured varispeed button of the CD player. Then I can record&play with any speed from -12.5% to  +12.5%.  It gives a click/pop when varispeed is activated but that can be removed later. I have looped a 88.2kHz project with +12.5% for half an hour and I did not hear any pops or clicks.
 
Btw. I tought the ABBA sound engineer  Michael B. Tretow used -0.5% tape speed for recording some of the vocals.  I probably misunderstood that.  I can only find info that he used ambience mic to do a second take of acoustic instruments. For this he used -0.5% slowed tape speed and mixed in the mid/highs to widen the mix. Maybe this made it sit better in the mix as it did not have exactly the same frequency spectrum components as the take with normal speed but to little difference to sound out of tune.  Some ABBA vocal takes  have probably been recorded with more than 0.5% slowed down tape speed.