Hello guys, i have a question

The alto trombone really helps you in that extreme high register or is just a very slight help,

If my tenor range is somwehere to C# D depending of my mood, the alto will help to hit that High F (Beethoven 5 high F) ?

The main advantage with an alto in high register is that the partials are farther apart. If you are having trouble landing on a particular partial in the upper range (often going too high or too low) the alto can help. If you can't play the note at all, the alto isn't going to help.

There are times when the sound of an alto is appropriate for the piece. I like using an alto on the few Mozart trombone parts, choral music, and Beethoven; but not because I need it to hit high notes.

Many people use a smaller cup and throat on alto, which can help the higher range speak easier. Also many use a narrower cup as well. It's somewhat of a different instrument from tenor.

I have a high F when playing orchestral tenor, and found that it was definitely easier to hit it consistently on my alto.

My main consideration for using the alto over the tenor is sound rather than range. On the alto I can “shine through” the sound carpet of the orchestra without covering up other instruments. My upper range is more or less than same on both instruments. May be it is somewhat easier on the alto but I get tired more quickly on alto as well.

As others have said, the alto probably won't increase your range (or endurance). The effects when playing vs tenor is that 1) the partials in the high range are spaced further out so it's harder to miss notes and 2) it takes less air to play because it has a more brilliant sound that makes it more noticeable in ensembles when playing in the high register and/or quietly

The alto has two big advantages over tenor:

1. There is easier access to the upper register that you already possess, and if you use the correct mouthpiece, your endurance up there can be better than on tenor...if you can play it in tune.

2. The slide is significantly shorter than a tenor trombone, and if you use the correct mouthpiece, articulations are easier on alto than on tenor. These advantages mean that it it's possible to play very technical passages on alto that would be extremely difficult or impossible on tenor. This has everything to do with not having to move the slide miles and miles during fast passages.

It has one big disadvantage, at least for tenor trombonists:

1. The alto doesn't have partials that line up like your tenor. Casual "doublers" can't play the thing in tune. It takes just as much knowledge and experience to know how to play alto in tune. If you don't, not only will the sound be horrible, but you'll be scratching your head, wondering why your chops give out after only a few minutes of playing with others in an ensemble.