Any Unknown or Unlisted Aircraft Manufacturer
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 20
Confusion; Communication Breakdown; Distraction; Workload; Time Pressure; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Separated Traffic
Procedure
I was Working LC1; LC2; LC3 and LA1 combined due to low staffing today when the traffic level spiked all of a sudden and the frequency overlap overwhelmed me.  I departed a Bonanza or Baron off Runway 34 Left for a left downwind departure to the South and gave the typical restriction of at or below 2;500 feet MSL till South of airport.  I was attempting to call and get IFR releases for aircraft and SCT wasn't responding.  I was also working a few helicopters on a different frequency than the fix wings and was getting frustrated at the overlap.  My Frontline Manager (FLM) mentioned SCT is not going to give you a release because of Aircraft Y turning final for BUR.  I was getting mad that I had no help and was essentially working everything.  I noticed the Bonanza (or Baron) turning downwind towards Aircraft Y who was at about 3;700 feet MSL descending eastbound when I told the Bonanza (or Baron) to stop his climb which he leveled off at 2;300 feet MSL and passed under Aircraft Y.  Right before this time I was trying to ask (not directly) my FLM if I'm supposed to avoid Aircraft Y or was it normal operations.  About 5 minutes later the SCT FLM called over and wasn't happy that I let an aircraft fly under Aircraft Y.  My FLM called down to SCT probably on outside line and they talked.Allow Ground Control and LC3 (helo's) to be combined once again.  Over half of my workload and coordinations would have been simply eliminated.  There is a reason GC and HC was combined for 40 plus years at VNY.
VNY local controller working three locals combined describes a situation where he isn't sure what to do and asks for help but doesn't receive a timely answer. Aircraft in the pattern flies underneath a VIP aircraft which leads the TRACON call to complain about the operation.