I have to digitize a 30 ips tape using a 15 ips machine. I'll of course need to render out a digital file at double speed for the client.

Back in the old days, there were many ways to render an audio file at double speed (or half speed), without performing any DSP/time-stretching/compresson. It simply read the file faster or slower.
I need not only to hear it, but to render a file, so changing clock speed won't work.

Thanks for any ideas.
We have PT, DP, Logic, RX

right. DAW's generally used to have the behaviour you describe and now seem to generally not have. I actually use Reaper here but it seems to be being found to be the same case with other DAW's and it also seems to be the case with Reaper.

I suspect that as many DAW's transitioned to include pitch shifting and time stretching, this old behaviour became problematic. potentially so problematic that it was largely removed as any kind of easy option to instantiate.

if you imagine a condition where projects regularly involved stretching and shifting, then switching in such a behaviour would likely play havoc with the project. so much so that they could easily crash, as all the stretched components would have to revert to all kinds of unknown conditions.

I'm speculating that this may be why it seems to have disapeared so roundly. Reaper seems to have a preference to indicate which items may be undergoing sample rate conversion, but I can't yet find any way to have the item not undergo it. only an indication that an item is undergoing it at the current projects sample rate.

Edit: currently trying playback of a 96Khz file in Reaper, just using the internal Audio system on a Mac. finding that when Reaper's Audio driver is set to request the block size of 96000 from the audio system, then the Audio Midi settings are forced to switch to that rate, when selecting that option.

However, the 96Khz sample seems to keep playing back at double speed, when either previewing from Reapers file browser or when dragging in the same file into the timeline.

trying different block size sample rates and it still seems to load and playback at the same rate, regardless of wether or not I change the preferences base sample rate or the projects base sample rate, with over-rides.

so far I can't figure out what would explain that behaviour.