Transitions are broken

[nkleemann]

No matter which orbit a pattern is currently playing on, after using any transition (like xfade or clutch), this pattern get's re-routed to d1.

How to reproduce:

-- plays on second orbit
d2 $ s "bd(3,8)" 

-- bug, now plays on first orbit
xfade 2 $ s "arpy*4" 

However, when orbit is excplicitely given, the bug disappears:

-- plays on second orbit
d2 $ s "bd(3,8)" # orbit 1
-- stays on second orbit, as it should
xfade 2 $ s "arpy*4" # orbit 1

In the Tidal Discord I uploaded a video demo: here

Tidal: 1.9.4
Supercollider: 3.13.0

[Zalastax]

I have found the source of the bug:

The definition of d2 is

Tidal/src/Sound/Tidal/Safe/Boot.hs

Line 66 in 6ffb9c4

d2 = p 2 . (|< orbit 1)

p is just streamReplace

Tidal/src/Sound/Tidal/Safe/Boot.hs

Line 33 in 6ffb9c4

p = streamReplace

And streamReplace replaces a pattern based on it's ID

Tidal/src/Sound/Tidal/Stream.hs

Lines 590 to 592 in 6ffb9c4

	streamReplace :: Stream -> ID -> ControlPattern -> IO ()
	streamReplace s k !pat
	= modifyMVar_ (sActionsMV s) (\actions -> return $ (T.StreamReplace k pat) : actions)

The implementation of xfade acts like a streamReplace but during a transition it fades between the patterns. Notice line 76 which is the end state where your new pattern fully replaces the original pattern

Tidal/src/Sound/Tidal/Transition.hs

Lines 74 to 77 in fcc4c5d

	xfadeIn :: Time -> Time -> [ControlSignal] -> ControlSignal
	xfadeIn _ _ [] = silence
	xfadeIn _ _ (pat:[]) = pat
	xfadeIn t now (pat:pat':_) = overlay (pat |* gain (now `late` (_slow t envEqR))) (pat' |* gain (now `late` (_slow t (envEq))))

But since your new pattern has not been modified by . (|< orbit 1), the orbit is lost.

I guess the best solution would be if instead of xfade 2 $ pattern you could write xfade $ d2 $ pattern or similar.