Bad sound for one line instrument (Very recent regression in 0.9.6 branch)

MuseScore r3118 (branch) on Mac and windows (can't reproduce on mac or windows with r3116 nor 0.9.6).

1. Open musescore on promenade
2. Create a score with 3 Congas staves, one hihat and one drumkit 5 lines

Press N

3. Select first instrument in drum palette
4. Enter a note

Actual result: Conga sounds like a piano.
Expected result : Conga sounds like a conga in 0.9.6