Jamieson, Fausset and Brown on Hosea 5:8

8. The arrival of the enemy is announced in the form of an injunction to blow an alarm.

cornet ... trumpet--The "cornet" was made of the curved horn of animals and was used by shepherds. The "trumpet" was of brass or silver, straight, and used in wars and on solemn occasions. The Hebrew is hatzotzerah, the sound imitating the trumpet note (Ho 8:1; Nu 10:2; Jr 4:5; Joe 2:1).

Gibeah ... Ramah--both in Benjamin (Is 10:29).

Beth-aven--in Benjamin; not as in Ho 4:15; Beth-el, but a town east of it (Jos 7:2). "Cry aloud," namely, to raise the alarm. "Benjamin" is put for the whole southern kingdom of Judah (compare Ho 5:5), being the first part of it which would meet the foe advancing from the north. "After thee, O Benjamin," implies the position of Beth-aven, behind Benjamin, at the borders of Ephraim. When the foe is at Beth-aven, he is at Benjamin's rear, close upon thee, O Benjamin (Jud 5:14).